I managed to solve the issue, as I found in Event Viewer that the action process got an DX9 error when trying to start.

The solution was to re-install my actual graphics driver!

Since 1 week action completely refuses to start. I use it on Windows 10 since about 3 Months without any major issues. Suddenly after I returned from my holidays, I tried to record a game, but Action just shows the Splash Sceen for a second and then just does nothing anymore. When I start Task Manag...