You've tried different settings in the multiplayer options, made sure your firewalls were not blocking access, etc?
A couple people in the alpha with connection problems reported being able to play co-op using something like Hamachi or Tunngle.
If you each email supportdos@larian.com, with a description of the problem and the report.zip file generated by the
D:OS support tool, the network (and other) info included may help Larian fix the problem.
The report.zip file includes your saves, so if the file size is an issue they can be deleted from the zip (not being relevant to the problem).
