Fortnite duos no correction?

Hey guys I want to play duos with a colleague but now the following problem. With us and all other people you can play normal duos. In the said colleague, everything is no longer displayed in the game modes selection. If I invite him and stop duos and he then presses Start, the button is gray instead of green and there it says that he has no correction for the mode. Can someone help?

Have you ever entered a custom game key? With how many people are you in a lobby

That could be because you have to play across platforms

if that's on then all modes will go off then solo only