Okay so I own the PMDG 777LR for P3D v3, but when I try to install it doesn't install because I get this stupid msg saying:
"Installation cannot continue. Your registry does not show a valid Prepar3D(tm) installation location"
I had the same problem with the NGX but I did something to fix it and when I tried to do it on the 777 it didn't work...
All I can do is to tell you to contact customer support and tell them exactly whats wrong.