I was playing on a realm and left because it was laggy. When I attempted to join back it said "there was a problem with your internet connection, try again." I checked my connection and it was perfectly fine, as well as i could join other worlds and servers and my connection worked just fine. This same thing happened to my other friend in the realm and they haven't been able to join back since the bug started happening. Everyone else on the realm is still able to join the realm just fine.