I’m not an expert in this area but i think some of the online subsystem steam only works in packaged for release you may try this as well and see
This may be of some help if you haven’t already been there
otherwise unfortunately i have no idea
another thing to check would be to make sure the steam app itself is allowed through the firewall correctly
for me i did this for my steam client it was already as it was supposed to be
and when i launched my game for the first time a popup appeared asking
here is a picture of what i mean that i just grabbed from the internet of course instead of java it would say YourGameUnreal or something i honestly didn’t pay attention when mine popped up
did your app ever have this popup?