Teams Desktop app not streaming camera to receiver, but is visible on the callers side

We are seeing an issue on a number of laptops when we make a call the camera in Teams will not stream to the recipient. 

The person making the call can see their camera in Teams as a preview in the thumbnail area whilst in the call so its not a permissions issue on the camera with the app.

• The issue only started after we upgraded to latest release for W11.
• Zoom and other apps load and stream the camera fine.
• Teams web streams the camera with no issue.

Where it gets really strange is if I call say from the Windows laptop to a Macbook - camera streams no issue

I then hang up and call another Macbook user running the same OS, Teams Version etc and it fails

I call another windows device it fails then call another Windows laptop it works. It always only works and fails on the same devices.

We have run through the following troubleshooting steps:

• Run and installed all OS updates
• The laptops are deployed via Intune and the laptops are running the latest versions of everything including Teams 2.x being installed.
• The issue is visible across multiple devices (Lenovo X1 Carbon, Dell 5450)
• The issue is visible across multiple networks on these devices
• There are no %appdata%\microsoft\teams or %localappdata%\microsoft\teams folders present to delete as the Installer is baked in to the OS apparently and installed through the Webapplications folder
• There are no C:\Program Files or C:\program files (x86) Teams folders to delete
• Hardware Acceleration for Teams has been disabled via Powershell
• We have tried different networks including hot spotting on all laptops, it makes no difference
• We have checked BIOS and disabled security on Graphics and I/O Virtualisation
• When the call is in place looking at the call stats for the laptop not streaming the video, the send packets, bit rate etc is zero
• Reiterating, when a call is made and the receiver cannot see the camera, the caller themselves can see their own video camera in the Teams call
• Have downloaded and checked the Teams logs during a call there are no H264, Media Stream errors or other concerning errors
• Tried reinstalling MS Teams with the 2.x machine wide installer
• Tried stopping and starting the relevant services
• The laptop has been restarted many times
• We have tried multiple profiles on the same device
• We have rebuilt some of the devices (factory wiped partitions - redeployed from MCT - Media Creation Tool)
• Pre-upgrade on W10 the cameras work with no issues
• Tried dropping the camera resolution to 720 in the camera app
• The built in windows camera app and all other apps show the local camera no issue
• We have tried using external USB connected cameras and the same issue occurs - only in Teams still.
• Using Teams Web the camera streams
• Zoom desktop works - not a local driver, hardware issue specifically tied to W11 running Teams 2.x
• We have run all driver updates from Manufacturer website (Dell and Lenovo after they scanned the devices) and Intel after scanning the local machine no change
• We have tried downgrading the integrated camer driver (not an issue though as external usb also fails) and also the intel graphics drivers

This seems to be more related to the Teams app itself and it being able to or allowed to establish a connection to the recipient Teams app that allows the camera stream to take place, for some it works others it fails. Is anyone else currently facing this?

To repeat again sorry as I know it will be asked:

• Not a profile issue
• Not a %appdata% or %localappdata% issue
• Not a Camera driver issue
• Not a permissions issue on the camera
• Not a graphics driver issue

Teams version where the user is calling from: 25198.1109.3837.4725

The Laptop in the above testing scenario is a Lenovo X1 Carbon 2 in 1 Gen 9 running OS version: 26100.4946

AI says:

Microsoft probably made a change in Win11 26100.4946 (or slightly earlier) in the Windows Media Foundation / WebRTC / AV1-H.264 negotiation pipeline. That change might require a matching update in Teams 2.x to keep P2P working, and the current production build isn’t handling the new API behavior in all cases.

If that’s correct, Microsoft will likely fix it in either: 

• A future Windows cumulative update, or
• A Teams 2.x hotfix update that adjusts how negotiation happens.