Operation out of stock (Bulk O.S) error: The quantity must be a valid number greater than 0.

Reason: If you click "Out of Stock "(Bulk O.S) to display an appeal error, it is probably because the main switch of "Out of Stock Settings" is not turned on.
Solution: Go to "Channels >Sales Channel", click the small gear icon behind the corresponding eBay account, and open the "Out of Stock Setting ", as shown below:

If you can't find the "Channels >Sales Channel" page in the system, it is recommended to contact the administrator or a colleague with permission to deal with it.