Overnight I forged around 16 heat now all day I have not got any is there a reason why
Think of it like lottery tickets. Each HEAT increases your chance to forge a block, sometimes you get lucky and get several blocks quickly, other times you are unlucky and will go longer than expected without forging a block.
Over time it averages out and should end up at 40% durring the first year, if you are forging all the time.