The direct explanation of the error content is:
The product category (eBay Cat) selected in the datasheet does not support Multi-Variations.

Solution:
If there is only one product category: It is recommended to try another category. If you refer to other people's variation listings, you should pay attention to whether the other party's "site and category" is consistent with the "site and category" you set in the datasheet , especially the classification of the two eBay sites of US and eBay motors cannot be used universally;
When two product categories are set: both product categories need to support variation listings, and if one of the categories does not support variation listings, it will also affect the listing.