Hey @foxhull hope you’re doing wonderful and I’m very happy to welcome you to the forums!
I’m sincerely sorry you’ve been experiencing this situation with the Steam deck unable to establish connection.
So far I’ve seen some other cases but most were resolved after installing the EAC Proton Runtime, in your case as for now you could probably try uninstalling the game and deleting all the related info and then trying once again with the EAC executable available for the steam deck.
I’ll proceed to look for further troubleshooting as well, but I’d heavily recommend you reach us. Let me know have you contacted us to escalate this situation with the following link?
This way our peers over can gather and request the proper information from you to dive deeper into this and to solve this situation.
Hope it’s useful, wish you a nice day and see you on Aeternum!