realms not working?

i recently (yesterday) purchased a realm for me and my friend(s) to play on, but sadly, whenever both of them try to join, it kicks them out. realm settings have changed since i've last played, and when one of my friends join, it says "you are not whitelisted on this server." the other friend can join for maybe less than a minute, then it will sadly kick him out.
i am unaware on how to resolve this conflict, but i've looked everywhere to try and figure it out! i'm pretty sure it's a bug, because i've tried everything to fix it, and nothing seemed to work.