When looking at SRS on the SQL Server everything was configured fine. In Reporting Services Configuration Manager a Service Account was set (a domain user, which is a best practice), and the Report Manager URL was displayed fine also. All ConfigMgr reports were displayed here!
First a few captures to display the issue:
A Windows domain user account is configured in RSCM
Starting the Report Manager URL shows no errors..
But no reports are displayed in the ConfigMgr console
Searching on the web I found an recommendation to use the Local system account as SRS Service Account. I changed above configuration from Windows domain user account to a Local system account and it's working again. Strange thing that Microsoft recommends to use a Windows domain user account, but it's not working that way.
The following captures displays the solution:
Configure the Service Account to use Local system in RSCM
After change have a look in the ConfigMgr console again
Nice to have 423 items in Reports again. Just use Local system in SRS Service Account from now on, to pass this issue.