"NO REBIS AVAILABLE TO USE" even with Rebis in inventory

I’m playing Witcher 3 Enhanced Edition (version 4.93), and everything is going somewhat ok, except I’m having some problems getting alchemy to work. I have lot’s of Rebis in my inventory, but when I try to craft potions (like Swallow) the game says "NO REBIS AVAILABLE TO USE" even though I have plenty in my inventory. What is going on here? Am I missing a distillation step or something?