Someone posted a fix in this thread but the post is now gone. Can confirm that this issue is fixed with IE version .12-77. It is fixed in both 12-78 and -79.
https://minecraft.curseforge.com/projects/immersive-engineering/files/2535471
From the changelog: "- Fixed Blastfurnace not working...
I have yes but thank you for your reply. I am pretty familiar with immersive engineering and its mechanics as its one of my favorite current mods. Just as an experiment to see if the ratio was adjusted by the mod pack I used a full stack of coal coke blocks to try to smelt one iron ingot. It...
Summary of the problem Immersive Engineering Crude Blast Furnace will not smelt iron into Steel
Pack Version 1.6
What is the bug? The crude blast furnace will activate when you put both coal coke/Charcoal and iron into it. However the progress bar will not move and the furnace will not smelt...