Add 4x Amazon Listing Variations

I have a parent listing with 16 variations. I want to add more variations but I'm getting an error saying that the variation theme (sizestyle) is no longer available for the category so I can edit current variations but cannot add new ones. I've spoken with amazon support who have been pretty useless. Can anyone help? I'd just like to keep my current listing that has built up sales on it but add 4 new variations. Please provide a quote and mention the word "Unicorn" to show you have read this brief. Thanks.