Super bummed

I borrowed my cousins Doppler from when she was pregnant (her beautiful daughter is 7 months old now) and I'm able to find baby's heartbeat with complete ease but for some reason the Doppler won't show the beats per minute. Originally it would flash for like a second but it doesn't show on the screen at all anymore and it really makes me sad 😭 I just wanted to rant! I love hearing it but I wish I could see how fast it was going!