Troubleshoot the Apollo Dialer: Why Do I Have Connection or Audio Problems With the Dialer?

Article author
Brandan Blevins


Do you have trouble hearing the person you're talking to on the Apollo dialer? Is your audio cutting out? Are you unable to make a call using the dialer?

There are several issues related to hardware, software, and network connectivity that can impact your ability to use the Apollo dialer successfully. But fear not! Apollo is here to help.

The following sections provide step-by-step guidance for troubleshooting your dialer issues:

Step 1: Check Hardware

Software issues are often rooted in the hardware you use. Start by confirming that your hardware provides the resources that the dialer needs to function properly. Apollo recommends you use a computer with at least 16GB of RAM.

Apollo also recommends that you use a USB-based headset when making calls. The latency in a wireless headset can cause delays.

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Step 2: Perform Basic Troubleshooting

With your hardware confirmed to be performing adequately, you should perform some basic troubleshooting for your software, specifically your web browser and operating system settings.

Troubleshoot Web Browser

Your web browser can consume too much RAM or cause other issues that result in poor connection quality. Try the following steps to improve your dialer connection:

  • Confirm that only 1 instance of Apollo is open in your web browser.
  • Close browser tabs that you don't need open. Too many open tabs can result in heavy resource use on your computer.
  • Make sure your browser is up to date. If you use Chrome, enter chrome://settings/help in the address bar. This page displays whether Chrome is up-to-date or provides you with an option to update it. Chrome

  • Clear your browser cache. If you use Chrome, enter chrome://settings/privacy in the address bar to view your browsing data. Then, click Clear Browsing Data.


Click the Time range drop-down and select All Time. Then, click Clear data to clear the cache.


  • Perform a hard refresh on your browser with the keyboard shortcut Ctrl+F5 for Windows PCs or Command+Shift+R for Macs. This clears the cache for a specific page.
Even More Troubleshooting Options!

Troubleshooting is not an exact science. Unfortunately, there are many ways in which your applications could stage a rebellion. Please read Troubleshoot the Apollo Chrome Extension for more tips on getting your applications back in your good graces.

Review Windows Network Settings

If your issues with the dialer are not related to your web browser, you should review your Windows network settings to ensure that Windows is allowing the needed network connections.

The 2 network settings that are most likely to interfere with the Apollo dialer are:

  • Windows firewall
  • VPN

Windows Firewall

If you have enabled your Windows firewall, it can interfere with the Apollo dialer. You can either disable the firewall entirely or whitelist Twilio's full IP and port ranges.

To disable your Windows firewall:

  1. Open Control Panel, then click System and Security. System and Security
  2. Click Windows Defender Firewall. Windows Defender Firewall
  3. Click Turn Windows Defender Firewall on or off. Windows Defender Firewall On Off
  4. Click Turn off Windows Defender Firewall for both private and public network settings. Turn Off Windows Defender Firewall

With your Windows firewall disabled, test your dialer connection again.

Whitelist Twilio's IP Ranges

If you can't disable your Windows firewall, check your firewall configuration.

Your firewall needs to give outgoing User Datagram Protocol (UDP) access to the public internet from the web browsers that use the dialer. The firewall also needs to allow return traffic in response.

If you are on a restricted network, you must whitelist Twilio's full IP and port ranges.

Going Through Changes

Twilio—the third-party provider Apollo uses to integrate voice calls—is updating its IP and port ranges. If you've enabled your firewall, you need to keep the old IP and port ranges open in your infrastructure until January 23, 2024. You also need to add the following new IP and port ranges:

  1. Add to your firewall rules.
  2. Enable UDP from these IP addresses over ports 10000-60000.

Once you’ve updated your network infrastructure, you need to enable your account's production traffic to use the IP ranges.

For more information about Windows firewall, please refer to the Microsoft learning center.

VPN Usage

VPN usage might also affect which edge server Twilio uses to route traffic. This can add some latency to calls. For example, if you are in the US trying to make a call to the US without a VPN, Twilio uses an edge location in the US to route the call. However, if you use a VPN that connects you to a server in Australia for the same call, Twilio might route the call differently and negatively impact the call quality.

If you use a VPN, there are 2 options:

  • Apollo recommends you disconnect from your VPN when making calls.
  • If you cannot disconnect from your VPN, you need to coordinate with your engineering or IT team to allow Apollo permanent access via firewall and VPN rules.

You should also confirm that your antivirus software is not blocking Apollo and the dialer.

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Step 3: Troubleshoot Specific Audio Issues

If you still have audio issues after checking your hardware, web browser, and network settings, you should troubleshoot based on the specific audio issue you are experiencing.

The following sections provide steps to take based on the specific nature of your audio problem.

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Audio Cuts Out

If audio drops intermittently so that you have dead air, you are likely experiencing an unstable network connection. The dialer requires a high-speed, low-latency network connection.

First, perform a speed test to verify your network connection speed. If your connection speed does not match what you pay for, talk to your internet service provider.

If your connection is on the slower side, follow these steps to improve your odds of a good dialer connection:

  • When possible, use an ethernet cable for your internet connection rather than a WiFi connection. Wired connections are more reliable.
  • Close tabs in your web browser. Tabs take up bandwidth.
  • Exit any other programs that use bandwidth.

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Unclear Audio

If you maintain a steady connection when using the dialer, but you experience a garbled or otherwise unclear audio connection, there are several potential issues to explore.

Follow these steps to try to eliminate your poor audio experience:

  • Use a wired headset instead of your built-in computer microphone. As with the internet connection itself, a wired connection will deliver a more reliable audio experience.
  • Reduce ambient noise, such as nearby speakers or fans.
  • To avoid audio clipping (a form of audio distortion), make sure your microphone isn't too close to your mouth.
  • Adjust the microphone levels in your computer settings. Your input may be too loud.
  • Ensure that your computer has sufficient memory to process the dialer. Apollo recommends that your computer have at least 16GB of RAM.
  • Close any applications that you don't need during calls.
  • Antivirus software can be resource-heavy. Try disabling your antivirus program while you make a call.
Stay Safe Out There!

Apollo does not recommend disabling your antivirus software unless it is a last resort to troubleshoot an issue. Keep your network and computers safe at all times.

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No Audio

Confirm that both your hardware and software meet all of the dialer's requirements. If you check and there is still no audio when using the dialer, Apollo recommends the following steps:

  • If you use an external headset, confirm you have attached your headset correctly.
  • If you are using a wired headset, try plugging your headset into a different port. Ports can fail without any warning.
  • Confirm you have selected the right device in your sound settings. For example, your computer's audio output might be set to your computer speakers, even when your external headset is connected to the computer.
  • Try connecting a different external headset.
  • The Apollo dialer integrates with Twilio. Run this Twilio-provided test to help pinpoint your issue. Twilio Test
  • Try a different web browser. If you use Chrome, try the dialer with Microsoft Edge or Firefox.
    Chrome Plated

    You can try a different browser to see if the behavior differs, but Apollo recommends you stick with Chrome so that you can take advantage of the Apollo Chrome extension.

  • Confirm you have given your web browser permission to play sound.

    If you are using Chrome, go to chrome://settings/content/sound and make sure you have enabled the Sites can play sound radio button. Chrome Sound Settings If you have customized which sites can and cannot play sound from your browser, verify that your computer has listed in the Allowed to play sound section. Chrome Sound Settings
  • Confirm you have given your web browser permission to use your microphone.

    If you are using Chrome, go to chrome://settings/content/microphone. Verify that your computer has listed in the Allowed to use your microphone section. Chrome Setting: Allowed

If is listed under the Not allowed to use your microphone section:

  1. Click the Trash Can icon to delete it from the list. Chrome Setting: Blocked
  2. Go to chrome://settings/content/microphone. Then, click Sites can ask to use your microphone under the Default behavior section. Enable Mic
  3. Follow the instructions in Make and Receive VoIP Calls. When you try to place a call, Chrome will ask permission to use your microphone. Click Allow. Allow Microphone

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No Ring Tone; One-way Audio

If you do not hear a ringtone when using the dialer to make a call, or only one side of the call can hear audio, this is likely due to high post-dial delay (PDD). This means Twilio sent a connection request to the telecom operator, but it’s taking a lot to respond.

PDD is most likely caused by the caller and receiver being geographically far away from each other. This means it takes time to establish a connection between the 2 parties. Using a VPN can add to the delay when establishing the connection. If you use a VPN, there are 2 options:

  • Apollo recommends you disconnect from your VPN when making calls.
  • If you cannot disconnect from your VPN, you need to coordinate with your engineering or IT team to allow Apollo permanent access via firewall and VPN rules.

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Ring Tone, but No Audio

If you hear a ring tone but no audio after the call is answered, the issue is most likely due to the telecom operator. Apollo recommends trying to make the call again later.

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Step 4: Enable Call Debugging in Apollo

If the troubleshooting guidance in this article does not fix your issues, enable call debugging in Apollo and then contact the Apollo Support team. Refer to "Configure the Dialer" to learn how to enable call debugging.

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