Problem:  While working on getting multiplayer setup,  players were not able to join another devices session through searching for a public match, they were only able to join via direct invite,  which is only what we want for private matches. There was also an issue that as soon as one player joined, the session settings automatically got updated to not be joinable anymore by any other players. For DeadlandsDuel, being able to have four players in a match is very essential because of our class system, and because we believe the game will be the most fun with all four players. We also want to be able to join matches from people on other networks, without an invite, public lobbies can be a big part of a game like this' community, and we want that to be able to happen. 

Solution: The issue with players not being able to join from public searching was happening because the game requires port forwarding on some ports for TCP+UDP, without uploading the game to steam, there is no automatic NAT punchthrough. I was able to get other devices in my own network to join via public match once I portforwarded for the device I want to host the server on. As for the issue of not being able to have more than the first two players, it was because I was misunderstanding a setting that you have to set when creating a multiplayer session. The setting is called, "CanJoinInProgress", since I was thinking ahead to when we actually get the main game loop networked, you would not want players to be able to join you while you are in the middle of a match, but apparently as soon as you invite someone to the lobby, it will automatically start the session. After changing the setting to true, we were able to get all four players in the lobby at once.