Nextcloud new user not popping up

hello all;
I am new to this forum and I hope someone will shed some light on it. I have not much experience in linux so would request if anyone is helping out please put full command.
ISSUE: I have added a new user to one of the domains. There is another domain which is in federal trust between both, and while sharing any file, we can find each other users. But only for this new user, I am not able to share file by searching his name from other domain… hope it makes sense? so if I domain A and domain B, there is a federal trust between both, and domain A users can share with domain B users and vice versa, however, I added a new user in domain A and domain B users are not able to find him, any idea why? Just to let you know domain A, went to maintainance mode for some reason and had to be upgraded.