Hi Kwamz,
Thanks for contributing to our forum. The reason that you have started receiving these API errors such as "Category 139971 only accepts custom item specifics" when attempting to post your items is because eBay recently stopped accepting the format of data that is used when information is entered in the product details fields available in the “Find Product” interface for this category and a few others.
Our engineering team is currently working on updating our system to make it so this data which eBay will no longer accept can no longer be entered in our system but, for now, you should be able to post these listings successfully by removing all the details from that section and trying again.
In order to be able to successfully post any of your saved listings that have previously failed due to one of these API errors, you should just have to click the Edit Product Details link within them, deselect ALL specifications on the following page, and then click Submit.
Once you have done so, you will then want to click the Custom Item Specifics link for the listing any enter any of the desired details you would like to add to the listing there. After that, you should be able to post the listing successfully.
Similarly, if you are going to be creating new listings for this category, you want to make sure none of the specifications are selected on the page you are taken to after you use the Find Product link to locate the item in eBay's product catalog. As long as you enter those details in the “Custom Item Specifics" section instead, your item should post to eBay.
I hope this helps. If you need any further assistance with your account, please feel free to contact our customer support team by mousing over the “Help” tab within your account and selecting the “File Support Case” option.
-Mike
