found the diamond key
but how do i restart my fire

The first thing I would do is this. I would start my game and click on "MENU". Down on the bottom left-hand corner, check which version of the game you have. It should say 1.00.04. This would be the latest version of the game. If it does not say that, please refer to this post

If you have 1.00.04 and you are still having problems, let us know here and we will try to help you out more.

Have you been able to put the key in the door? If so, just start the fire as normal. If not, see the guides section for how to pick up the key.
[SPOILERS] VV3 Puzzle Solutions & game tips.

Oh what an "ELDER" I am.
Figured it out.Just had to drop a villager on top of the fire pit.
Thanks for the quick reply.