We (gog) finally managed to find 3 players for a MP match and had the following issue:
3 players - 2 with gog version - 1 with steam and gog version available
all on 1.0.33
steam updated normally to 1.0.33 (this was a few days ago). gog versions updated with vault patch.
routers/ports/connection were configured correctly and tested.
we tested all configurations and found out the following:
steam can NOT connect or host to gog versions (screenshot below)
only gog versions are compatible with one another.dont know whats up with vault versions.