So I'm trying to fight that chair, but it keeps telling me none of my pets can fight. The pet I wanna use has everything full, so I'm really confused about why it won't let me do anything?

Try checking your Statistics page and seeing if your pet isn't already in a battle. That's usually the issue if you're unable to get it to show up.

Thanks. I don't remember putting her in battle but oh well. I'll remember that next time!