CustomPress taxonomies not functioning with MarketPress

I created two CustomPress taxonomies, brands and occasions, for my MarketPress products. When I create a new product or try to edit an existing one, the new taxonomies show up, but they don't function.

If the taxonomy is set up as hierarchical, the choices appear but the checkboxes are not checkable. If the taxonomy is not hierarchical, only the heading (e.g., "Brands") appears. (I actually want both of these taxonomies to be non-hierarchical, but I set the occasions taxonomy to hierarchical as a test.)

This appears to be similar to the issue discussed in this recent thread:, except the custom post type involved is "product," as created by MarketPress.

I have seen multiple recommendations on WPMU DEV to use CustomPress to add custom taxonomies for MarketPress products, so as far as I can tell, this should work.

Screenshots are attached, showing (1) that the product post type is selected for the custom taxonomy, and (2) how the custom taxonomies appear on the product entry form.

Please advise. Thanks.