Report Server to PBI Report Server upgrade - Subscription issues

Hello,

We have been running an early version of Report server 2016, using the standard ReportServer and ReportServerTempDB databases.

I made restores of these databases with different names, ReportServerPBIX and ReportServerPBIXTempDB.

Installed PowerBI Report server and pointed to these new DBs.

things appear to run just fine apart from when trying to save subscriptions it is throwing the below error.

ERROR: Microsoft.ReportingServices.Diagnostics.Utilities.ReportServerStorageException: An error occurred within the report server database. This may be due to a connection failure, timeout or low disk condition within the database. ---> System.Data.SqlClient.SqlException: The server principal "NT SERVICE\PowerBIReportServer" is not able to access the database "ReportServerTempDB" under the current security context.

But ReportServerTempDB shouldn't be used anymore! It should be pointing to the new version. When I do a SQL data search (text search in Apex SQL) for ReportServerTempDB in the ReportServerPBIX database, there appears to be lots of values pointing to the old TempDB.

All our subscriptions are now broken :(

I am guessing one solution is to remove/rename the old reportserver + reportserverTempDB since they are not being used now anyway. Then rename the PBIX ones into their place, and update Report Server Configuration Manager to point to this renamed DB's.

Be nice if there is just something I could simply update in the database without having to rename stuff and potentially break other things.

Would appreciate some pointers/suggestions to resolve this please.

thanks