Just buy EU3 and Collection Upgrade. After hitting the play button on the Paradox launcher, the screen get black, then back to desktop, then black again with the hourglass crusor, and finally get back to desktop without running the game.

I used the Verify & Repair function of GoG Galaxy. 300MB of game files was downloaded, but EU3 keeps crashing.

I tried to start the game without the Paradox launcher but it doesn't help. I'm running on Win10.

EU3 works well if I disable the Collection Upgrade... But let's face it, I won't play without it !

EDIT : Problem solved by disabling and downloading the DLC again !