Coop not working

Hi everyone. Excuse my english it is a second language.

My gf and me bought the game two days ago since it looked fun.

Now we can't get the coop to work. We live together and we never had a problem with any multyplayer game. Our internet connection is working fine.

In Temtem our characters don't move, the other players don't move aswell. This means we can't play together.

Is there a solution to this that does not involve paying for a VPN or changing my internet plan with my provider?

We are on PS5.

Thank you for reading.