*P.S.*: DESYNC FIX
Search for "Powershell" and run as admin. Copy and paste each line separately and press "Enter" key each time (so 5 times total). On the last line you should get alot of lines randomly. Then you did this right:

md $Env:TEMP\certs

cd $Env:TEMP\certs

CertUtil -generateSSTFromWU $Env:TEMP\certs\RootStore.sst

$file=Get-ChildItem -Path $Env:TEMP\certs\Rootstore.sst

$file | Import-Certificate -CertStoreLocation Cert:\LocalMachine\Root

Right click MK11 in game library and go to "Properties" then "Installed Files" then "Verify Integrity Of Game Cache". Then regret fixing online because you're going to start raging in the next couple minutes

Credit to "FinanceRelevant9013" on Reddit

good

This game's mulitplayer does not function on the current version of Windows 11. It is a known issue with no fix besides downpatching Windows. If you attempt to play multiplayer on Windows 11, you will disconnect due to desynch within seconds of game start every single game.