I had a dead lamb last week. Ewe looked very quiet all morning, kept have little pee, by lunchtime she was pawing the ground, up and down, etc. By 9pm I was panicing and pulled out a dead lamb followed by a live lamb. If she is showing signs of labour, pawing ground, taking herself off to a quiet spot, lying down, getting up etc, and not producing then you could have a problem. But if nothing at all is happening, she might not be ready.