welcome to HCM
you have to repeat the test again.
at this time heart rate
should be picked up by doppler.if in second scan it comes negative then better to consult a gynecologist and get a detail clinical examination
when you did your last scan?was that scan was postive for intrauterine pregnnacy?if it was positive then there may be some problem to fetus.dont neglect. consult your doctor now and follow her advice