This help article explains the error 21916799 given by eBay. When you get this error in your listings, Sumtracker is not able to update the inventory of these SKUs.
Here is the error shown by eBay on the inventory errors by numbers page
Short error: SKU Mismatch
Long error: SKU does not exist in Non-ManageBySKU item specified by ItemID.
Kindly note: eBay is a complex platform having multiple types of settings. Understanding how eBay functions can be difficult for us as well. Please reach out to us if following the steps in this article does not resolve the issue for you.
Why does this occur?
One of the most common reasons why you could be getting this error is that you are trying to revise a variation that has already been removed from the Channel Item. For example, you listed a product with a variation ‘Size L’ with quantity 4. Later, you revised it with quantity 0. When you updated the quantity as 0, the SKU got removed because of eBay settings.
If you try to update the variation ‘Size L’ with any quantity, you will now get error 21916799 because the SKU doesn't exist anymore. You need to update the product on eBay and add the variation back on eBay with the same SKU.
How to resolve this for future?
Enable Out-of-Stock setting for the listing.
To enable the out-of-stock setting for an eBay listing, you can do the following:
Go to My eBay
Click Account
Click Site Preferences
Under Selling Preferences, click Show next to Sell Your Item form and listings
Click Edit next to Use the out-of-stock option
Select the checkbox
Click Apply
Once enabled, the out-of-stock setting will apply to all existing and future listings. When an item's quantity goes to zero, it will remain in the listing but won't appear in search results until it's back in stock.
What does this mean?
If Out-of-Stock setting is disabled, eBay removes a SKU when the inventory quantity for the SKU listing reaches zero.
When the quantity is updated to zero, the SKU is removed. If you try to update the SKU again, you'll receive an error because the SKU no longer exists.
eBay's default minimum listing quantity is one, so any sold-out listings must be stopped. However, you can use the Out-of-Stock control setting to hide sold-out listings from buyers instead of stopping them. The listing will become active again when you increase the stock.
This article explains how eBay handled the variations based on the Out-of-Stock setting.