It's less of an arc furnace specific thing, more that: the only block of steel that is available is the AllTheOres one, but that doesnt seem to work in immersive engineering multiblocks. Specifically: I cannot figure out how to make these blocks (Block of Steel)

I tried using steel slabs stack on each other - didn't work. I tried using the AllTheOres steel block - didn't work. Whenever I click on the cauldron, I get nothing. Is anyone else having this issue?

hol up i did something wrong when building it - it might be a me thing xD lets see

yeah. wow. i cant believe i didnt notice that before. this has been an issue for SO LONG - my bad! glad it works