I got a message that none of my pets were eligible for battle, even though my main pet WAS, so I put the others in the resort. Now THEY are showing up as eligible for battle, but my main pet is nowhere to be seen, even though she is bloated and happy and her health points are full.

Have you checked your Battle Statistics page to see if the pet is already in a battle that hasn't been completed?

slaps head I'm definitely having a d'uh day today! Thanks, I can't believe I forgot to check that!

You're welcome, and I'll go ahead and lock this. :)