Cause
It is an expected error as the default behavior of the CTX system parameter FILE_ACCESS_ROLE has changed.
Solution
1. (Recommended) Create a new role, grant it to the owners of the impacted indexes, and set file_access_role to the new role.
- or -
2. Set file_access_role to 'public'
To change file_access_role, you must be connected as SYSDBA.
SQL> connect as sysdba
SQL> exec ctxsys.ctx_adm.set_parameter('file_access_role', 'public')