Minecraft Version

1.12.2

Forge Version

14.23.5.2768

Mod Version

1.12.2-0.8.1-274

Describe your problem, including steps to reproduce it

The recipe to craft a Diamon with a Block of Coal doesn´t work. I tried it with a Block of Coal, single Coal, and also with Charcoals Variants. But the Diamond won´t be craftet. The Condition are set, but the Pressure chamber won´t work. In generell they work. I can put iron bares to craft compressed iron or other recipe.

You need 8 blocks of coal to make a diamond, not one.

If jei is showing the wrong recipe, try upgrading to 0.8.3 (which you should anyway - there are many bug fixes).

Closing this - as far as I can see there's no issue with diamond crafting. Just be sure to use 8 coal blocks.