eBay has a list of reserved words for some categories which cannot be used as a label for a custom option or associated product. When listing a product with variations you use one of the reserved words, you'll see the error message: "The tags … is/are disabled as Variant".

For example, you used the word "Style" as a label for options but this word is reserved by eBay in a particular category. You’ll see the message  "The tags Style is/are disabled as Variant". To solve the problem, you need to change the option label " Style" to "Product Style" so that eBay system wouldn’t consider it as a reserved word.