Dying Light - Can't join?

My wife and I have been trying to play Dying Light together on the XBox One for hours, but no matter if we start again or take the memory from 12 months ago, there's always the message "The game session you wanted to join is not more available "although it is very available. Do you know what we can do 😥

Restart the console
Check Internet connection
Set up Internet connection again
Restart the modem
If LAN cable is present, check this
Maybe reinstall game (quite unlikely that it is because)
Have you two already completed the prologue?

Oh how cute a pair of gamblers. Can you watch sometime on RTL in women exchange?

Have we already done everything twice and yes we did the prologue. For security even started again and looked at it is probably the old memory but nothing, no way to get in 😭

Do you both have Xbox Live Gold?

Without that it is not possible to play online