If you receive an error message stating that ‘Steam is already’ running, open up your Task Manager and check if a process of FM is already open. If there is, click on it and select [End Task] to close it. If there are multiple instances of Football Manager 2020 being open, please close them all. Once this is done, try re-launching the game.
If you still continue to have problems, please read the troubleshooting techniques below to resolve the issue.
First of all, please see this 'Steam i