For months? I assume you're not in cloud-only with your org. and perhaps not in Teams-only mode either.

This should be verified with your IT admins and perhaps with the official support really. I am attaching a couple of links to start with.

https://docs.microsoft.com/en-us/microsoftteams/exchange-teams-interact
https://docs.microsoft.com/en-us/microsoftteams/presence-admins
www.000webhost.com