Work down these. The first three account for almost all of it.
1. It is still a draft
The commonest by a distance, especially after a bulk import — every imported row lands as a draft and stays one until you publish it. A draft is invisible to everyone but you. Listing a lot of items quickly
2. It has no photograph
An imported row with no picture stays a draft deliberately. Add one and publish.
3. It is not on sale
A listing can be off sale without being deleted — check whether it is active. If you took it down yourself, put it back on from your listings.
4. It expired
A fixed-price listing runs for 30 days and then needs renewing. An auction with no bid goes stale after 30 days. Neither deletes anything; both need you to put it back up, which is free. What happens to items that do not sell?
5. The buyer cannot be reached
Not a fault. A show or an item from a store that cannot deliver to somebody's PIN code may not be shown to them — a filter, not a ranking. So a listing invisible to one person can be perfectly visible to others. How are shows ordered?
Check your zones cover where you expect buyers to be. How to set delivery zones
6. Metzee took it down
The only one that is a problem, and you were told — a notification naming the reason, and it will not go back on sale. Why was my item taken down?
Trying to relist it gives you a message saying so rather than failing silently.
What is not the reason
Being a new store. Nothing is held back while you prove yourself.
Not having paid for anything. Listing is free and no promotion is required to appear. Do sellers pay to appear higher?
Search being slow. If it is published and on sale, it is findable.
If none of these fits
Raise it under Listings & inventory with the item. How to raise an issue
The check worth doing first
Open your own store page while signed out, or on another device. What you see there is what a buyer sees — and it settles in ten seconds a question that is otherwise guesswork.
More: what happens to items that do not sell, why was my item taken down, my bulk import did not work.