Description of the issue:

When crafting fireworks in the Assembler, it ignores reagents. Testing with other recipes it's fine, but I noticed also that the fireworks recipe does not show up in the minecraft recipe book. So perhaps it's related to that?

Happens both in singleplayer and on multiplayer. I tested it also standalone with only forge and IE installed.

Versions & Modlist

ImmersiveEngineering-1.16.1-4.0.0-118.jar
forge-32.0.108

Yes, the recipe is valid. But it's creating the rockets without any materials.

I see nothing wrong with that, that is a valid recipe according to https://minecraft.gamepedia.com/Firework_Rocket.