If you are receiving this error or a variation of this error:
'Item cannot be accessed because listing has been deleted, is a half.com listing or you are not the seller'
It may be confusing because it mentions half.com.
Half.com was an online marketplace owned by eBay Inc. that specialized in selling used CDs, DVDs, VHS tapes, video games and books at bargain prices. It was officially shut-down at the end of 2017. But this fact probably has nothing to do with this error.
What this often means is that the item being accessed is no longer available on eBay. eBay deletes old listings after 90 days, give or take a few days. Especially if stock remains at 0 after 90 days.
When you post an item on eBay with Hyperspace it is 'listed'.
When an item sits on eBay with no stock for 90 days, it is 'un-listed' or deleted by eBay.
That is an eBay rule and it cannot be changed.
When you replenish your 0 stock in Lightspeed Retail (From 0 to >1) Hyperspace will attempt to re-list the product. In fact, there is even a button called 'Fix Ended Listing' in Hyperspace. You can use this button to force an ended listing to re-list.
If you try to re-list a listings that has already past the 90 days and stock has been 0 during that entire duration, then it may no longer exist on eBay. It has been "deleted" by eBay.
There error means that you are trying to re-list an item where stock has been 0 for over 90 days and it is no longer on eBay. It cannot be re-listed with the same ITEM ID.
You will need to create a new listing on eBay for that item.