I'm on The TerraFirmaCraft Starter Pack through CurseForge.
Following the guide book given I tried to put 10 small Limonite I had found on the surface in a Vessel to make 1 wrought iron pickaxe head, to be able to progress.

Problem: When the small vessel comes out of the pit kiln it stays on yellow-white** and never reaches white, when right clicked to open interface for casting it says "Too hot to open!"
Eventually it cools back to 0 heat again and then the ore inside is just completely unsmelted.

Any other thread I found on this says either completed or solved but yet this is still a problem for me.
I updated to the latest version for the main mod TerraFirmaCraft and the problem remained.

We use the issue tracker for bug reports, not support requests, please use our discord for those. You're clearly not following the guide book because nowhere does it say limonite, can be melted into wrought iron, in a pit kiln.