The 18.12.2 must be clean installed (use the custom clean install option in radeon installer or DDU).
There is a new hotfix driver 18.12.3, try that (clean install).
Did you run DDU from safe mode and did you use the latest version from a few days ago?
Did your restart with the INTERNET DISCONNECTED?
Then install the driver you already have downloaded?
These are all key to it working.
Same , Version 18.12.2 and 18.12.3 don't let me open AMD radeon settings . Now I only can update display driver and audio driver and keep using AMD settings from version 220.127.116.11