Well, I can not tell for sure. I am a lawyer...
Something like this:
1. Turn win 10 to a previous version (without creator).
2. Run net cleanup tool trying to uninstall .net framework 4.7; no success.
3. Uninstall win update KB40416764 (very important, I think).
At this point PF3 still do no work. I wondered if something in the default configuration was the problem. So, I created a new user, reinstall PF3 and adjust the addons (GSX, FSUIPC and so). Windows usually do what it please, and start updates without previous warning; to prevent that, I deactivate win updates under win services. And, voila! PF3 works perfectly.
I believe that you always was right, Dave. Creator was the problem. But something in default configuration blocked all modifications that I was trying to do. Making a new profile solved the problem.
One testing fly... all perfect. Back in business.
The important thing is that you were always here giving assistant Dave. You guided me somehow. So, thank you, thank you very much.
Cheers from a very satisfied customer,