The Snipe Tool (Snipe It button) is added to your browser, not to your eBay account, and will only show up on eBay auction items.  You will not see the Snipe Tool button on Buy It Now items, as they cannot be sniped.  If you no longer see the Snipe It button on your eBay auctions, you're using a different browser, reinstalled your OS (Windows, MacOS, etc.), or have a new computer.

To add the Snipe button back to your eBay auctions, please visit the Snipe Tool page and follow the directions to add it again to your browser / device.