Import Export Custom Taxonomy

I have a ton of products to add to Shopperpress and am trying to fit my product data into the same columns used by WordPress to import everything. I tried manually adding a couple products and exporting them using the Shopperpress tools “download csv” feature. But the custom taxonomy selections didn’t export.

How do I import my values for custom taxonomies? I tried the column heading as csv_ctax_brand for example to populate the product brands custom taxonomy, and the import worked. But the brand didn’t get selected.

Anyone else know more about this? Thanks!