Second player in multiplayer cannot be controlled

I recently got the PlayerBuildingSystem by DefuseStudios for free, and it says it was multiplayer compatible, so I decided to try to make a game with it. I add the join and create session code to the game from the default create project menu in the epic launcher, and I tried a lot of things to make it work. The host player works perfectly, but and clients will be able to see and see other players but not move the camera or the player… Is it a common issue and how do I fix it? Thanks!