If the listing has not been deleted, is not a Half.com, and you are the seller this is a very confusing error. Thankfully, it is can be easily fixed.
This error normally appears if you try to relist/revise an item which ended more than 60 days ago.
Another reason for this - if you changed eBay account in the Listing (i.e. item was listed with one eBay account, then you change account and try to perform activity using another eBay account)
Go to the eBay edit listing page for the listing suffering from this error
Click the action button and then end and relist. This should mitigate the issue.
Celebrate your healthy listing!