In the Microsoft 365 Connection Settings, admins may face an error message informing that the the "(...) refresh token has expired due to inactivity".
This message is displayed in case the course catalog has been inactive for a certain period of time and no email notifications were sent from it. This activity is required in order for the token to keep refreshing itself.
The default lifetime for tokens is 90 days. Tokens replace themselves with a fresh token upon every use, so in case of inactivity, no fresh tokens are obtained.
To find more information on the refresh token functionality, please see Microsoft's documentation on Microsoft identity platform refresh tokens.