Cannot host a singleplayer/coop session

[Gavinrad]

I don’t know if you still have issue, but I had the same problem, which i resolved. Here is the specific way to open the ports you need :

Cannot play with my friend in coop mode

I didn’t understand anything about ports at first either I’ll try to help you as much as i can. So, I’ll screen what i did : 1- type firewall to get access to it. [Capture%20d%E2%80%99%C3%A9cran%20(1)] 2- When you’re in, go to where i put the red box (sorry, it’s in french )[gsgsd] 3- then, next red box: new rule [fffff%20-%20Copie] 4- go on port [gqgqg] 5- Then TCP, and you put what’s needed here : 25575,27015-27030,27036-27037 [gqgs] 6- Then autorise the connection 7- …

Hope you sort it out !