I have the latest version installed (Mekanism-1.12.2-9.8.3.390) on both my server and client, However none of the fussion reactor blocks like the reactor frame shows up. It doesnt show up in Just enough items and when I try crafting it, it just doesnt output anything. I can still craft other mekanism blocks.

Do you have mekanism generators installed?

Oh, I didn't know I needed that, My bad.