What does this error mean?
If you see this error, eBay has temporarily "blocked" editing the listing to make sure the listing info stays the same for certain buyers.
The error is a direct message from eBay that essentially says
a buyer is interested in your item,
a buyer is trying to buy your item,
or a buyer has purchased it recently
and making changes to a listing would be against eBay policy during this time.
How to fix the error:
you will need to end the listing and relist the item.
For fixed-price listings,
check for open offers and resolve them.
otherwise, the error will go away on its own in a few days when eBay allows the listing to be updated.
Why does eBay block listings from being edited?
eBay does not want users to be in the process of receiving or buying items with the item details changing. This protects sellers and buyers from miscommunication about the listing.
What if I don't have any offers or bids?
eBay's AI may also determine if you can edit a listing based on internal factors. While eBay's inner-workings are proprietary, eBay is very smart and could possibly be engaging buyers to purchase your item, or has noticed that a buyer has added your listing to their shopping cart.