Importing products to Marketpress with Custompress custom fields

When I import products into MarketPress, the custom fields (created with Custompress) aren't populating. This was working originally, but now it's not, and I'm not sure what might have changed to break the functionality. I have customized a couple of theme templates, and also tested importing a checkbox & radiobox field. After those fields didn't work with the import, I went back to just text fields, but now no custom fields seem to work.