I can't battle my pet Luchador, it says he's not fed or happy enough.

But he's bloated/very happy!

... Sure he is... Deadbeat!

I have the same problem:( I'm not a battler, so maybe I messed something up lol? Is there anywhere we can read the rules of the Battle Coliseum?

Check and see if your pet is stuck in another battle. Look in Statistics in the Battle Coluseum. If they aren't stuck or you can't withdraw them, then start up a Help ticket.