Dead Island Definitive Edition Co-op problem

I'm a little puzzled why there is no resolution for this problem. It would appear as though it's been going on for quite some time based on the results of my searches, and now you can't even get support from Deep Silver or Techland. I just purchased this
game during the recent sale in anticipation of playing with friends, only to find out it does not work. There's no problem with the Quick Join - servers are still working for that. Every time I try to join a friend's game or they try to join mine it errors
out with some message about the session no longer available. This was really a fun game on the 360, but I feel like I've been robbed for the Xbox One version. It's not a lot of money, but it's the principle of being sold something that does not work as advertised.

Does anyone know of a solution that solves the co-op connectivity issue? I've tried all of the recommendations that I could find, including delete/reinstall, checking router settings, Xbox settings, etc.

:)