Just went to play X4 this morning and the game refuses to launch. I get no error messages. When I double-click the X4 icon on my desktop, the box pops up indicating that Steam is preparing to launch X4, the box disappears (as normal) and then... nothing. The game worked fine 4 or 5 days ago when I last played. I recently got a new video card (Radeon RX 580), but I have played X4 since installing it. AFAIK no new Radeon driver was installed in this time, and 2.0 was installed when it was running previously. I have followed the instructions on the Steam community page about deleting some of the setup files, but that didn't help. I have just updated the video driver now in the hope that it will fix the problem, but I doubt it. I'll reboot now and if it fixes the issue, I'll update. I have the day off work and was going to play with my son, so this is kinda frustrating to waste my day on.
