Using Shape Builder in Pattern Editing Window

Hi!

I'm trying to use the shape builder tool to fill a shape in the pattern editing window. The Shape Builder tool and Live Paint Bucket tool both have the "no" symbol next to the cursor, even when the enclosed shape is selected. Are these not options when editing patterns? Both tools work fine on the shape when I go back to my artboard/workspace. 

To clarify - these cacti are made out of multiple shapes to meet the project specs - normally I would build them out in a much more sensible way. 🙂

TYIA for any help!