If you have a Microsoft Teams room and are setting it up for the first time, or even had a recent update, you might have seen this banner on your system.

The question is, what caused this or how do I troubleshoot this? While the system seems to work, it just does not show the calendar of the logged in account and some have had difficulty knowing where to start.
 

COMMON CAUSES

There are a few common causes and most of the time you see this when first setting up the unit, but it has shown up before with some customers with a hybrid deployment due to autodiscovery as well.

CHECK YOUR SETUP
Make sure that you have looked at the setup of your account and you have followed the suggested setup per the Microsoft Documentation found here. There is even a PowerShell script to enable making the account correctly even easier and it can be found here. You can also find a full article on making the account by Jeff Shertz found here.

CHECK THE AUDIT LOGS ON THE ACCOUNT
You can look to see the attempts to login to the account in the Audit logs on your O365 tenant and that will more than likely tell you why the authentication is failing. You can find out more about checking the audit logs here.

CONDITIONAL ACCESS POLICY’S
Check to see that you do not have any conditional access policies that might be blocking the MTR system from authenticating if you have the mailbox in O365. There is a very good article on conditional access found here.

MAKE SURE YOU HAVE THE MINIMUM VERSIONS FOR THE SYSTEM
The minimum version of software might also be at fault here. The minimum that the MTR units support is Exchange 2013 if you are running on-prem in a hybrid deployment.

AUTO-DISCOVERY ISSUES
While this is not frequent, I have had an issue where auto-discovery was flagged in the logs of the unit and needed to be addressed in DNS within the organization.

BLOCKING PORT 443
Units will need access to HTTP ports 80 and 443. TCP and UDP ports configured as described in Port and protocol requirements for servers for on-premise Skype for Business Server implementations, or Office 365 URLs and IP address ranges for Microsoft Teams or Skype for Business online implementations.