Teams: Yealink MP50 unable to start, answer, or end calls

Hello,

I recently deployed some Yealink MP50 USB phone devices to my agency users who are on Teams Voice. For some, the MP50 works perfectly: plug and play and away we go.

Unfortunately, for most users they can't start, answer, or end calls but the pause/resume and mute/unmute work fine during a call.

• If they start a call from the phone's controls it looks like it is attempting to dial out but nothing happens on the PC and it eventually ends
• If they receive a call it shows up on the MP50's screen but the answer and decline buttons do not work and neither does pressing speakerphone or picking up the handset.
• If a user starts or answers a call on the PC they can use the MP50 for microphone and audio
• Picking up the handset switches it from speakerphone to handset,
• If I do a test call on the troubled setup, Teams displays a banner saying "No device call controls. Exit other calling apps so you can use your device call controls with teams.

I have worked with Yealink support through a lot of troubleshooting, but unfortunately have not resolved the issue. I will give a rundown of the troubleshooting.

• Our Teams accounts are in Teams only mode and we do not have Skype for Business
• I have troubleshot the issues for a couple of months, so it has persisted throughout Teams updating
• I have troubleshot on a couple of different firmware versions of the MP50
• For those having issues, I switched them to a device that worked on another PC but it didn't work on theirs
• For those having issues, I took their device and put it on another PC that had a working one and it worked there
• I've tried multiple device resets
• I've deleted out all drivers out of device manager and reinstalled it, multiple times
• I've tried completely removing Teams and all files/folders from the PC and then reinstalling and setting up Teams

Here is a rundown of some extensive process of elimination troubleshooting I did, with users A and B

• MP50 works on user A's setup but not user B's setup
• User B logs into their Teams account on user A's PC with user A's domain account logged in, the MP50 works
• User B logs into their Teams account on user A's PC with user's B's domain account, the MP50 works
• User A logs into their Teams on user B's PC with user B's domain account logged in, the MP50 doesn't work
• User B logs into their Teams account on user B's PC with user A's domain account logged in, the MP50 works

To me, this eliminates the possibility of the device, the PC, the Teams accounts, and the Domain account from being the issue and just leaves it to being an issue with the local Windows profile on the PC.

I hope someone can provide some other troubleshooting options. I may have to look at alternatives, but what from I've seen it sounds like most other phones run Teams as a separate instance, creating several other drawbacks, or else have to be dumbed down to operate similar to the MP50 which makes them a waste of money.

Thanks