"No data found" in APEX export/import utility
I recently upgraded my system from DB 11g EE via 18c EE to 21c EE. APEX was upgraded from 5.0.2 via 5.4 and 18 to 23.1. I am using THOTH Gateway, not ORDS. Everything is in Windows Server 2016.
Before upgrading everything I had no issues but now when I try to import applications/plugins/components etc though the built in APEX import/export utility I get the error message "Error uploading export file. ORA-01403: No data found". I have tried creating new applications and exporting them. The export works fine but importing them back in fails.
The strange thing is that I have no problems running the exported sql files directly in the database and importing my applications that way, but using the import utility in APEX App builder is not working.