[Darryl Ramm]

... OK a quick look, as much time as I can spend looking at Windows. I have a Windows systems that used to have a recent-ish install (2019.6??) on it..and the old plugin directories still there, and it seems has a similar issue as well at least in that past install, I can't run a 2019.12 install there now.

C:\Program Files\Common Files\Avid\Audio>icacls Plug-Ins
Plug-Ins Everyone:(F) <--- Oops !
         Everyone:(OI)(CI)(IO)(DE,Rc,WDAC,WO,GW,GE,GA,RD,WD,AD,REA,WEA,X,DC,RA,WA)
         Everyone:(I)(F)
         Everyone:(I)(OI)(CI)(IO)(DE,Rc,WDAC,WO,GW,GE,GA,RD,WD,AD,REA,WEA,X,DC,RA,WA)
         NT SERVICE\TrustedInstaller:(I)(F)
         NT SERVICE\TrustedInstaller:(I)(CI)(IO)(F)
         NT AUTHORITY\SYSTEM:(I)(F)
         NT AUTHORITY\SYSTEM:(I)(OI)(CI)(IO)(F)
         BUILTIN\Administrators:(I)(F)
         BUILTIN\Administrators:(I)(OI)(CI)(IO)(F)
         BUILTIN\Users:(I)(RX)
         BUILTIN\Users:(I)(OI)(CI)(IO)(GR,GE)
         CREATOR OWNER:(I)(OI)(CI)(IO)(F)
         APPLICATION PACKAGE AUTHORITY\ALL APPLICATION PACKAGES:(I)(RX)
         APPLICATION PACKAGE AUTHORITY\ALL APPLICATION PACKAGES:(I)(OI)(CI)(IO)(GR,GE)
         APPLICATION PACKAGE AUTHORITY\ALL RESTRICTED APPLICATION PACKAGES:(I)(RX)
         APPLICATION PACKAGE AUTHORITY\ALL RESTRICTED APPLICATION PACKAGES:(I)(OI)(CI)(IO)(GR,GE)

Successfully processed 1 files; Failed processing 0 files

C:\Program Files\Common Files\Avid\Audio>cd Plug-Ins

C:\Program Files\Common Files\Avid\Audio\Plug-Ins>whoami
darryl-w10\g         # Thats a "guest" account "g" with no administrator privileges

C:\Program Files\Common Files\Avid\Audio\Plug-Ins>copy nul test
        1 file(s) copied.