I was going to throw a punch at that big Gelatin and it says:

Oh no! None of your pets are eligible for battle. You might want to make sure that they're well fed and happy!

But my battling pet is bloated and happy...

Has anyone encountered this?

http://subeta.net/games/battle/stats.php

Check under your battle's pet name, if it's already in a battle

- Well Good grief...and I kept trying to stuff more food in my pet! :) Thank you, that was it!!