It is a glitch but it's not impossible to make. I'm playing on the Enhanced edition on Steam. It has something to do with the fact that it requires 2 quebirth and 2 hydragenum. Switching around ingredients seemed to work allthough I could not pinpoint the exact solution. Basically I quicksaved and switched the ingredients around till it worked.
To quote someone called 'yourself_' from 13 years ago on gamefaqs (this forum doesn't let me post any links): "After playing with it more, I think I know what's going on. When the substances are auto-filled for Thunderbolt, if two of the same ingredient is used, the game doesn't recognize that creating the potion will detract 2 from your inventory instead of 1. So when you try to make what it's telling you is the max amount, you actually can't make that many. For example, if I have 10 Nekker Claws (Hyd) and 10 Mandrake Roots (Que), the create dialog will allow me to choose to make 10 Thunderbolts, even though in reality you can see that I can only make 5. But when I do this, instead of only making 5, it makes NONE and the items appear not to have been used (though if you check your inventory they'll be gone). Basically the moral of the story is MAKE THUNDERBOLTS ONE AT A TIME."
I took the time to write this cuz many related posts from the witcher 2 subreddit are no longer visible and Thunderbolt is a game changer if you're on the alchemy tree.
