I believe it’s related to Teams app version as they are running Teams app, which will require the version is matched between each other.

Current troubleshooting suggestion:
1. Check Teams app version for both devices from Teams admin center.
The latest Teams app version can be found here Release notes for Microsoft Teams Rooms - Microsoft Teams
If they are not latest version, even they are not same version, please update both devices to latest teams app version.
YeaA30 example:
CTP18 example: