After you apply security update GDRs 4532097 or 4535706, the SQL Server 2016 Reporting Services (SSRS 2016) URLs become case-sensitive, and you may be redirected to the home page of the portal if the URL is incorrect.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
This issue is fixed in the following cumulative update for SQL Server:
About cumulative updates for SQL Server:
Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. Check out the latest cumulative updates for SQL Server:
Learn about the terminology that Microsoft uses to describe software updates.