Causes:
1. The watch battery is low.
2. The watch battery is over-discharged if it has not been charged for a long time.
3. The abnormal system software results in a black screen.
4. Watch for hardware problems.
Solutions：
1. Charge the watch for 10 minutes and turn it on.
2. If the watch is not used for a long time, turn it on after charging for 1 hour.
3. Long-press the power button for 15 seconds to reset the watch.
If the above troubleshooting cannot solve the problem, please bring the purchase certificate to the realme service center.