Numerous tests have shown multiplayer matchmaking timeout errors

I tested it for several hours over 10 days considering nationality, preferred language, and minimum number of people, but multiplayer does not proceed due to timeout.
Cooperative multiplayer is possible with invitation sessions, but
It’s unknown how the original developer focused on the multiplayer intrusion method, but while this error issue has been reported by tons of players since the first Steam platform launch in 2019, the developer simply allows all players to select the multiplayer option in singleplayer. are doing Claims to be playing an invite-only game.

In single player, I set the multiplayer option to allow anyone to enter and no one entered my room for 10 days,
At the same time, it is clear that there is a problem with the matching system when you see that there was a multiplayer match on the Steam forum and the entry was not accepted.

Developers are aware of this and do not match any specific conditions with the host PC.
Do only the 1st matching for similar quest sections or levels, and if this condition is not met, please quickly patch the multiplayer matchmaking method so that anyone can match and invade.

This is the result of 10 days of exhausting all methods against any variable, and developers are obligated to quickly improve and patch bugs for players who pay for the game.

Any firewall settings that may blockade you?

Did you try to create a support ticket?
https://support.generationzero.com/hc/en-us/requests/new

There is no firewall, and the same content was re-submitted.