MHP3rd friend can't connect (hamachi)

[Boufi]

Hey guys, i've been playing mhp3rd with some friends recently, waiting for monster hunter world to come out on PC^^
We did manage to play quite a while actually until we tried again today, and it didn't worked for one of my friend. Of course, we checked firewall stuff, disabled every single thing that could hurt, even opened up 27312 TCP ports on our internet boxes.
This problem only seems to occur in this game tho, as we tried to connect on MHFU after that and it worked fine.
On AdHoc server, (i have the standalone version) it just says that my friend tried to connect and then he disconnected, no error message for him either.
I don't really know if there is any troubleshooting files i can send to you to check the problem in details.
Oh, yeah, if you're wondering, we're both on PC, i'm running windows 7 and he is running windows 10.

I'd also like to point the fact that we're running a JP iso that was partially translated in English cause we can't read JP, may this be the problem ?

Thanks in advance for your answer
Boufi