Issue with hosting a match with one friend

[Very High Cat]

Hey. I'm having issues with one of my friends joining my match. Whenever he tries to join it says "Unable to join game session". However all my other friends can join me. But when one my other friends hosts the match he is able to join them. So it appears that he is able to join everyone but me. But he is the only one who can't join when I host (custom match).

[hindercanrun]

@GaySeasalt host needs an open Nat type

[Very High Cat]

For anyone else who may have this issue, the fix was having your friend open a Command Prompt as admin and have them run the command

sfc /scannow

then fully reboot their machine. After he did this, he started being able to join. Hopefully this works for anyone else.