Please, answer / ensure the following:
0.) Using any mods, or have you ever used any in the past?
1.) Do a verify / repair through Steam / GOG / Origin.
2.) Be sure the game is not installed anywhere under
Program Files or
Program Files(x86). These are protected directories in Windows and it can introduce issues, even using standard Administrator accounts. Best bet is to install all games to the root of the drive or a folder of your own creation, i.e.
C:\The Witcher 3\... or C:\MyRPGgames\The Witcher 3\... (If using Steam, you can simply follow these steps for
moving an existing Steam installation. You'll likely have to verify each of your games once after doing this.)
3.) Add the game to the exceptions list for your anti-virus, firewall, etc.
4.) Set the game's .EXE to "Run as administrator". If using Windows 10, be sure that the Permissions for the game's folder and the
...Documents\The Witcher 3\... folder are set to "Everyone".
If that all fails, you can send a report into CDPR:
http://en.cdprojektred.com/contact-support/
or
Ask around in Mod Discussions for the code -- you'll likely get a faster response there. I recommend trying the steps above first, though, as forcing a quest can sometimes affect other areas of the game.
