Can't add variant products to Order from Admin

In FluentCart, all products with variants are greyed out when creating an order from the WP Admin > Fluent Cart > Orders > Create Order screen.

There is no interface to further select a variant. If I use the search bar, all variant products are greyed out and cannot be added.

Am I doing something wrong here?

NOTE: I verified that the product had an enabled Shipping Class and Tax Class.

I tried creating a brand new product (without variations) and this worked fine - it appeared in the product selection shown in the screenshot and I was able to add with no issues.

What is happening here? What am I missing?