After a long chat and about an hour of troubleshooting, the Adobe Support person and I solved the issue. It appeared that the "AdobeInstalledCodecsTier2" folder had permissions that were not staying set (we checked the boxes, but they became unchecked on their own). It tells you what the issue is: "make sure you have write access to this location..." The support guy used Command Prompt and the "net user" command to create another administrator user. After that, I could swap to the other Administrator account and launch Premiere Pro. I checked the "AdobeInstalledCodecsTier2" folder for the "mc_enc_hevc.dll" file, and it appeared twice. After this, I transferred back to my primary account, and the files were still there. I launched Premiere and everything worked. Hope this helps.  ... View more