Is it inside or outside? Maybe the fire needs more ventilation for smoke.
The Charcoal Kiln was there since the game went live its not part of the Hearth and Home just saying.
Anytime you see this it may require higher roof and or more ventilation.
Takes time to create coal a few secs not instant. keep adding wood if needed.
Mine is outside. Go do something else till its done.

It needs a huge chimney or be placed outside.

Just place it outside.