Can't Join A Guild

My friend can't join my guild; I sent them 3 invites but they can't join.
It is definitely not full please help.

 

Hi there! Is your friend still in a guild? Is he's still in a guild, he needs to leave the guild in order for you to send a guild invite.
If he's not in a guild, try changing worlds, as sometimes the guilds are buggy on certain worlds. If you are playing on an EU server, try switching to an American Server (WC world - eg. WC7, not EU world, eg. EU7)

Other bugs that you might encounter on European servers include:
Pressing tab, and finding out that "you are not in a guild".
You can fix this easily by changing into another world, preferably onto an American server. If you swap from an EU world to another EU world, I strongly recommend that the person go onto one of the WC worlds instead.

 

EU server must be buggy, I tried once this afternoon it worked first try, thanks.