Topaz applications not installing with installbuilder

I have a new iMac, with Catalina.

Had issues installing 3rd party software, seem fixed after fixed an issue with symbolic link to private/tmp

Now, can't install Topaz Studio, or Gigapixel.

Seems the installer doesn't even start running. As if blocked by my Mac.

Can't see the certificate in Keychain Access; should I?

{I am admin, and opening app from trusted developer, supposedly. Prefs set for this, not just apps from app store.]

Done a few things, like tried safe boot, tried different admin account, reset Home folder permissions.

Don't have antivirus software.

A few emails back and forth with Topaz about this; not closer to a solution.