Install FAILURE - repeatedly

I am a Local Admin.

I have explicitly created a User from my Windows login, and it has sysadmin privileges.

I cannot get past this message (Error 27506) whatever I try, and there’s no guidance I can find on the Support pages thus far.

REQUIRING an EXCLUSIVE lock on the model database – WHY?

I’ve email support several screenshots of contradictory installer vs. website installation guide issues.

Hoping for a remedy – 6 years of successful usage horribly marred by this roadblock.