UT Co-op Rivals lobby error - Failed to join game session

Hey everyone,

So I’ve been trying to do UT Co-op Rivals with my friend (he’s on PC and I’m on PS5), but whenever I try to join his party it gives me the “Failed to join game session. This session is already full or is no longer available, please try again” error message. We’ve got round this in the past couple of weeks by unfriending and re-friending again, but now there’s a bug where we can’t add each other as friends again.

We’ve never had this issue on last year's game but with this one we’ve had no luck with anything we’ve tried.

Can anyone help as to what we should do?