I know a lot of folks are having a plethora of "different" issues with "different solutions" that seem to fix a lot of "different problems". I thought I would share with you an issue I've had all day & was just able to figure it out after several hours of tweaking, research,etc.

Specs:
Win 7 X64
Nvidia 970 4GB
12GB RAM
Core i7
28" IPS panel

Problem:
Game fails to launch AFTER patching to 1.03. Double clicking the icon shows a spinning circle & then nothing. Opening task manager shows the application running as a process. Re-installed the game and patched to version 1.02, game works perfectly & launches fine. Then attempt to patch to version 1.03 & then 1.04 same problem game now wont launch at all.

Solution:
Please keep in mind your mileage may vary as numerous people have tried numerous things & all sorts of different things worked for some & not for others. Here is what I did & it's working great now.
Install the game & patch it up to 1.04 after successfully patching to latest version go to the following path (C:\GOG Games\The Witcher 3 Wild Hunt\bin) & add a ".OLD" to the folder called "ddi" (Example: ddi.OLD) this folder houses a DLL file called "GOG.DLL" that was preventing my game from launching after patch 1.02.

***WARNING*** Remove the ".OLD" BEFORE UPGRADING to next patch because it will completely ruin your game. The patch will partially complete and then give an error message saying it failed with errors pointing to "C:\GOG Games\The Witcher 3 Wild Hunt\bin\ddi.OLD". You can not run the patch again & the game must be completely re-installed. Good luck!