Hello
Actually, problem with Antivirus Avast on Steam / Gog Version PC of the Witcher 3
If you can't start the game, check in Antivirus (AVAST for example) :
text of alert with the file GFSDK_SSAO.win64.dll,
It's False Positive, you can resolve this bug :
1) edit the line of Security : Exception and restoration file
2) In gog / Steam, check cache of Filegame
3) Download again the witcher 3
It's OK to play
Actually, problem with Antivirus Avast on Steam / Gog Version PC of the Witcher 3
If you can't start the game, check in Antivirus (AVAST for example) :
text of alert with the file GFSDK_SSAO.win64.dll,
It's False Positive, you can resolve this bug :
1) edit the line of Security : Exception and restoration file
2) In gog / Steam, check cache of Filegame
3) Download again the witcher 3
It's OK to play