Watch the video:
Timestamps:
0:00 - Explanation
0:25 - Updating through Steam
0:50 - Windows Time is out of date
1:40 - Verifying game files
Want to play Rocket League, but can’t connect to servers, join friends or play games because your game is showing the Version Mismatch error? Well, this video shows you all you need to know about fixing this error. Your game is simply out of date, and by the end of this video, you should have done everything you can to make sure that it’s updated and working properly.