We are running SQL 2016 SSRS in native mode using the web portal. If a user is part of the local administrators group (windows) and runs a report they have permission to, the report works correctly and renders within an expected period of time (in most cases, 3 seconds). If the user is NOT a member of the local administrators group (windows) and runs the same report, it will eventually run, but it literally is "Loading..." for 10 minutes or longer. I kid you not. If I add that user to local admin, it takes 3 seconds. Remove the user from local admin, it goes back to 10 minutes or longer. Any suggestions? I've burned 2 days on this bad boy and I need to get this server into production.
Things I have tried:
Adding the windows user as a sysadmin on the SQL instance that has the ReportServer databases on it. That didn't help.
I also looked at the ExecutionLog3 view and the TimeStart and TimeEnd are match when the report actually does show up. So, as an example, I launch the report at 3:14 and it finally works at 3:24ish and the execution log shows a TimeStart of 15:23:39.020 and TimeEnd of 15:23:39.260.
Any assistance is appreciated.