Voip phone no audio

[alfee]

Valerie modem suddenly blocking the audio of my voip phone. I'm using the exact same setting for almost 3 years, never an issue until now. Port forwarding was setup since day 1. Already reboot the modem multiple times. Still no audio. SIP-ALG is always off. Any idea what else I can do? 

[VirginPlusAntonie]

Hi everyone, 

We would like to start by thanking everyone for bringing this to our attention and for all of the provided information and troubleshooting you've all made.

While this is still being investigated to prevent these issues in the future, our technical team have made a couple of temporary changes that should address the concerns at this time. 

For everyone that is still facing the issue, please reboot your modems (unplug for 30 seconds) and test your VOIP service to see if things are back to normal.

Please let us know if the issue is still present. 

Thanks.

[Sylvain]

2025-05-04 11h59 -> Issue still present here, Modem rebooted and ASA also.  Just tested on a Grandstream HT801 to the VOip.ms service.  The IP connecting on the  PdP server side (SIP) is in the 142.x range and the port is dynamic (Port #64040 as of now). One positive, outbound dialing now works, meaning the outgoings call have a dial and they ring.  But once the connection is extablished, still no voice.

[Sylvain · Accepted solution]

2026-05-07 16h00 -> Solved, no need to change my ATA settings, reboot the Virgin modem. Solution came from the ISP (virgin side).  Big thanks to @VirginPlusKris and @VirginPlusAntonie  for their patience and support for debugging this SIP "no-voice" issue.  After a modem reboot, the SIP ports are still shown as "dynamic" in the PdP server, but the line, tone and voice are working perfect.  Tested on a Grandstream HT801 with the VOip Wiki recommented settings with VOip.ms provider.  Still in IPv4.

[bigguy]

It did not work for me.  I tried it numerous times.   However I tried unplugging it for 10 or 15 minutes then it did work.  The problem is how will I know when the phone isn't working?  What do I do if I have to make a 911 call?

[61108743]

Hi 

I am still having same issue. Rebooted modem. Reset ATA. Still no Audio.

[VirginPlusKris]

Hi there, @61108743. Thanks for reaching out.

As with others earlier in the thread, we'll be happy to flag your account for further investigation. We'll be reaching out in a private message - Please check your Messages within your profile avatar in the top right corner.

Unsure how to check or send a private message? See How to send a private message

— Kris

[Jimmyc]

I have the no audio problem on a comwave HT502 ATA.  Are Kris and Antonie able to help me?

[VirginPlusAntonie]

Hi there @Jimmyc ,

Welcome to the community and thanks for reaching out.

As with others earlier in the thread, we'll be happy to flag your account for further investigation. We'll be reaching out in a private message - Please check your Messages within your profile avatar in the top right corner.

Unsure how to check or send a private message? See How to send a private message

Thanks.

[sunvright]

Same no audio issue.  Using voip.ms.  Using voip.ms softphone with no audio when connect using Virgin internet.  Using voip.ms softphone with cell data network have no issue (have audio).  Home ATA device was works before and now also have no audio when using voip.ms for calling.  Please flag my account for further investigation.

[VirginPlusAntonie]

Hi there @sunvright 

Welcome to the community and thanks for reaching out.

As with others earlier in the thread, we'll be happy to flag your account for further investigation. We'll be reaching out in a private message - Please check your Messages within your profile avatar in the top right corner.

Unsure how to check or send a private message? See How to send a private message

Thanks.

[slam86]

My VoIP stopped working suddenly. I have the Vincent modem and the Grandstream ATA HT502. My VoIP provider said the issue is due to Virgin Plus now using CG-NAT. Could you please tell me how to fix the issue? I called the technical support, and they had no idea what CG-NAT is. Please address this problem otherwise I will have to switch ISP. Thanks!

[VirginPlusAntonie]

Hi there @slam86 ,

Welcome to the community and thanks for reaching out.

We will be happy to flag your account for further investigation. We'll be reaching out in a private message - Please check your Messages within your profile avatar in the top right corner.

Unsure how to check or send a private message? See How to send a private message

Thanks.

[Rdc2]

Please let us know the status of the ticket tracking the actual fix for this.  It has been six months. 

Telling us to call you every 3-4 weeks in order to  reboot the modem is simply not acceptable. 

Thanks in advance

[slam86]

Hi Rdc2, does calling Virgin Plus tech support to reboot the modem temporarily fix the no audio issue with VoIP phone for you? Thanks. 

[beanieman · Accepted solution]

I've had this "no audio" issue for a few weeks.

TL;DR: I unplugged my Virgin modem for about 2 minutes (the suggestion above was 30 seconds from @VirginPlusAntonie), and audio started working again.

Important note: I had already rebooted my Virgin modem/router and VoIP devices several times without resolving the issue.

I contacted chat support, but the issue was too complex for first-level support and would likely have needed to be escalated.

After a lot of troubleshooting, I narrowed the problem down to the modem/ISP path.

[No audio]
VoIP Device → Virgin Modem/Router → Virgin ISP Network → VoIP.ms

[Works]
VoIP Device → Cellular Network → VoIP.ms

[Works]
VoIP Device → Cloudflare WARP → Virgin Modem/Router → Virgin ISP Network → Cloudflare → VoIP.ms

I tested two different SIP clients:

• Grandstream WP816 Wi-Fi VoIP phone
• VoIP softphone on my iPhone

The fact that Cloudflare WARP immediately restored two-way audio strongly suggested that the issue was somewhere in the normal Virgin network path rather than with my devices or VoIP.ms.

I also analysed a packet capture from the WP816. It showed that:

• SIP signalling completed successfully (REGISTER, INVITE, 200 OK, ACK, BYE).
• The WP816 transmitted RTP (audio) packets.
• The WP816 did not receive any inbound RTP packets.

Since audio failed in both directions, it appeared that the RTP media path was being disrupted. Whether this was related to CGNAT, filtering, gateway state, or something else, I don't know.

After finding this thread, I tried power-cycling the modem for more than 30 seconds, and that immediately resolved the issue.

I'm still not sure why it worked, especially since I had rebooted the modem several times previously. Perhaps the longer power cycle caused the modem to re-establish its session or pick up updated provisioning from the network, but that's only speculation.

Hopefully this helps someone else who runs into the same issue.