A multiplayer game is a  hard feat for a one hour and a half game.  The game had some networking issues, maybe next time refine the multiplayer first, before stepping into the rest.  Try maybe to start next time with a 2D project as its much easier to manage in this time frame, also I think you might be using a template off the unreal asset store, it would be good for your programming skill to at least use the code you wrote yourself. But good luck on your next game, I wish you the best, maybe try a smaller project first. 

Hey guys, I haven't rated the game, yet, I can't figure out how to make a server, it keeps throwing out "FAILED TO CREATE SESSION: *session name* " When I try to play. And I don't think there's a singleplayer option.

Edit: After reading the page, I figured out I need a steam key. However, I'm just trying to play Singleplayer..