After upgrading Exchange 2016 CU19 to CU23 which completed successfully. Exchange PowerShell no longer works and cannot be connected to. All IIS pages (OWA,ECP)are no longer accessible and throw HTTP error 500 same as PowerShell.
The Server is in a DAG and was first to be upgraded, all other servers work fine. Using ECP Management Page unable to modify virtual directory of upgraded server with access denied error.
Although database copy is healthy and replication is ongoing. Only front end services seem to be affected.
To note I have reviewed the exchange setup logs and everything seem fine. Event viewer does not display any out of the ordinary errors.
I have run exchange troubleshooter and it was able to connect to the server PowerShell, although launching the exchange management shell does not work.
All certificates are present and up to date.
Tried to assign valid certificate to Back End Website in IIS and still no luck.
Grateful for any ideas or direction to check.
Thanks