Can not play CO-OP on Nintendo Switch, Diablo III

Hi all,
I have a digital Diablo III and trying to play CO-OP and I can not make i work. I have done the following:

To play co-op on a single system with non-seasonal characters, you have to disconnect from the Diablo III server via the option in the pause menu. By this point this should allow the second account on your Nintendo Switch to join. The only time the second account can’t join is if the difficulty of the game is higher than what the second account is allowed to access. If both accounts have access to the online membership for the Switch then you can just skip the process of having to go offline.

The system says: “you can only select certain users” and all accounts on the switch are greyed out.

Do any one know how to fix it? Blizzard just says it should work and that I should ask you guys.