["Failure | ErrorCode:17000\ShortMessage:Lot Size is invalid. LongMessage:Lot Size is invalid, need to be greater than 1, and less than 10000."]
Explanation and solution:
By definition, a lot is a set of two or more similar items that must be purchased together in a single transaction. So, eBay doesn't allow you to list a Kit with a single lot (single quantity of component). You cannot list a Kit with a single component as a set of 1 and the amount of component that make the Kit should be more than 1 like a set of 2, set of 3, set of 4, etc.
For example, if you are trying to list a Kit of Tyres, you cannot list a Kit with just 1 tyre in it, the Kit will have to be made of multiple tyres like Kit of 2 tyres, Kit of 3 tyres, etc.