Items in the xxx category may only be listed using the classified ad format

The reason for this error is that eBay bans this category to be listed in the usual AUC and BIN formats. It can only do the Classified Ads listing. This error is more common in German sites.

eg: 

Items in the Motorsensen-Zubehör category may only be listed using the classified ad format

There is only one listing method that can be selected when the products classified above are directly listed on ebay.de 

Optional listing methods for the normal situation of product listing are as follows  

Since 'Classified Ads' format is not an auction or fixed price format that SoldEazy can be listing, if the product cannot be launched due to classification restrictions, the user can only change the classification or directly launch the product in eBay backend.