I am trying to play Portal 2 with a friend, but every time I attempt to play it simply says that my partner disconnected. I accepted an invite from my friend , after I invited him first, but received the same error. I have browsed the steam support page, but found nothing in relationship with my error and portal 2. I have validated my game cache with 1 file in question. I re validated again and found that one file was still missing . I do not have an issue connected with friends in any other online play and do not know what the issue could be other than this one missing file.