Nostalrius Begins - Quality wow vanilla realm (1.12)

Hi everybody, forgive me if this topic is somewhere in the forums, I have been looking but haven't found it.

I am unable to join any guild, if an invite to one comes up, I press accept and the popup goes away but I'm not in the guild I had just agreed to join, it's happened quite a few times now in the past day or so since starting my character. It's quite perplexing. Has anybody had this issue and/or has a solution to get around it?

I'm playing the Mac client on OS X 10.10.5 if that has any relevance. Thank you in advance.

By "quite a few guilds" or "any guild", do you mean the same guild repeatedly? Maybe a guild that has 321 members in it already? If that's the case, they are at the cap and can't take more members.