I have this frustrating issue where the "add to cart" form isn't appearing in my content, for a content type.

I've added the product reference field, and it was showing up at one point.
These are things I have thought of, and checked in:
- permissions
- product types
- product entity settings

I have looked over configurations, and done a search for a solution - no dice...

Any ideas for why a product reference field/"add to cart" form won't show up in the content type?
Things I could check?