Exchange 2019 Hybrid, Calendar button missing from Teams

After installing the CU11 Nov patch (15.2.986.36) the calendar button is missing from Teams. This has been previously working for over a year.

We have ran the Hybrid configuration again, done on all pre and after checks, all has come back fine.

We ran through the Oauth config again and OnPrem and Teams after communicating successfully.

Out of idea's other than update to CU12 or Jan CU11 update.