APEX Issues After converting to Multitenant Architecture

 

After converting the database to a Multitenant architecture, the APEX login page is visible, but upon entering credentials, the following error appears.

                          

This is a known issue with Oracle after converting to Multitenant


FIX - 
1. Login to Pluggable Database
2. alter system flush shared_pool;
3. alter system flush buffer_cache;
4. EXEC DBMS_UTILITY.COMPILE_SCHEMA( schema => 'APEX_210100', compile_all => TRUE);
5. Restart your Web Server