Only one client is travelling to next level, others fail

I’m using blueprint and I’ve been really struggling with multiplayer stuff the past few days, countless hours and no progress, that painful limbo phase.

I 've got one client being able to host a game/create a session, which another client can get into/join session, but whenever the client that’s hosting launches the game they’re the only one that ServerTravels to the level successfully, the other fails?

I’ve used a print string plugged into as much as i can, it says the second client failed to connect due to a network error on the client side, I have no idea how to fix this, desperate for any help,

Thanks