Yes, this horse has been beaten to death. Try this thread https://shoalsummitsolutions.com/forums/topic/error-on-installation/ or this one https://shoalsummitsolutions.com/forums/topic/activation-of-league-manager-causes-wp-admin-to-crash/
The problem is the version of PHP. Check your version and check the WordPress requirements.
Let me know if that doesn’t fix it.
-Mark