What does this error mean?
The error is a direct message from eBay. They are telling you that either:
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.
If you see this error, eBay has essentially "blocked" the listing from being edited.
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 decline 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.
"Description cannot be revised for
style listings that have
at least one pending bid
or are ending in less than twelve hours,
and for fixed price listings
that have at least one quantity sold
or have a pending best offer."