HALion Sonic is not part of the software that is included with Cubase Elements, correct?
Also, I completed everything you mentioned as well as reinstalling Cubase 10.5. All was well. Then I tried to install the 10.5.20 update. The old problem reappeared. I had to go through all the steps mentioned. I am not updating to 10.5.2. It loads HALion software then gives me access denied errors which are catastrophic.