Exchange ECP - The website was not found
After installing the CU5 for Exchange 2019, I was no longer able to log in to the ECP.
After a review it turned out that the authentication method for the ECP was changed.
With the Powershell I was able to fix that quickly
Set-EcpVirtualDirectory -Identity “SRVEX \ ecp (default web site)” -BasicAuthentication $ true -FormsAuthentication $ true
Then I was able to register again at the ECP.