A little more information is needed.
1. How deep is the valve, relative to total depth?
2. Did slickline catch but could not pull, or not catch?
3. Is a packer set? In other words, does the tubing currently communicate with the casing?
Generally, if slickline cannot pull something of this nature, there is either a pressure differential across it or scale. That brings on the next question, how stout is the fishing neck? Braided line may get it, but I would first try to determine if there is a differential across the valve. You may need to pressure up on the tubing above the valve, or swab the well down then pull the valve.
Biff
Clifton S. Partridge, P.E.
steelepetro@yahoo.com
601.807.8279