Looks like Exchange may not be signing in, typically you would see the room name under the time it it has successfully signed in. I would check your exchange settings in the admin side of the MTR. Is your exchange environment on-prem (which version) or O365? If on-prem you might need to load a certificate into the unit.
One good test to verify accounts is sign into the admin side of the unit, open a web browser and test the credentials here:
https://testconnectivity.microsoft.com/If you are comfortable perusing though logs you can pull a set and have a look for the the Teams and Exchange negotiation that is happening. Usually you can spot why it is failing fairly easily. The logs are quite verbose and easy to read.
