I keep getting the "Joining game session" bug and idk how to fix it

[Com. Pepperoni]

I just installed plutonium and when i want to play with my friend, this bug keeps appearing and it doesn't let me join him and it doesn't let him join me.

Pls help.

[ilytwo]

Com. Pepperoni Can you provide a screenshot/video or maybe explain a little more in depth? Is there an error?