Friends unable to join my Realm without buying a realm

I invited a couple of people to my realm and they are new to Minecraft. They had a pop-up saying they had to buy a realm and the popup wouldn't go away for them to accept my invite. They had to do a free trial just to join my realm.  I liater had an issue with a player saying he was whitelisted and couldn't get on. As a last resort I deleted him front he realm and went to readd him and has the same issue with him when he went back into realms.  Except he had to buy another realm as he owns his own server. Don't know why this is happening hope it isn't permanent.