Our advice to always to use FNSKU labels. When using the stickerless program, you can have a bad seller put counterfeit products into the stickerless pool that can go to your customers. Stickerless may seem easier to begin with, but the disadvantages may wind up costing you. FNSKUs guarantee that your customers get the genuine product that you paid for.
If you have a listing previously created when you had (for example) "stickerless" enabled with stickerless inventory sent, if you then change this back to stickered/FNSKU, you need to create a new listing (so Add a Product, same ASIN, new SKU) AFTER the settings have been changed. And vice versa.