Rocket League: Version Mismatch Please Get the Latest Version of The Game (Easy fix)
VERSION MISMATCH. PLEASE GET THE LATEST VERSION OF THE GAME.
If you're unable to play Rocket League due to this message, it means your game is outdated. To fix this issue, please download and install the latest update for Rocket League.
The easiest way to trigger the update is by restarting your platform. After restarting, the update should download and install automatically.