Hi Donna,
Can you please let me know the report name you are running.
If you had upgraded from a version which used DWH and was able to view the reports, I dont see a reason why you should not be seeing in 15.3.
Can you please check if the check boxes under DWH Options are checked.
https://docops.ca.com/ca-ppm/15-3/en/administration/configure-the-data-warehouse-and-advanced-reporting-domains
In the above URL, search for Configure the Data Warehouse
The setting is under Administration - System Options(under General Settings) - Datawarehouse Options

Please run Load DWH full load after checking the boxes.
Thanks,
Jerin