New users don’t show up in subsite of a Multisite

Hello,

When I add a new user in multisite, the user is successfully displayed in multisite super admin environment.

But when I go to the subsite where I want to add this user, the new added user doesn’t show up. (In the database the new user exists.)

Do you have an idea, why this happens?

(I exported the subsite from another multisite environment to a single site and imported it to the new multisite environment. So I am not sure if the error happend because of that. The old users are all there and everything is fine with that.)