If the heart rate measurement fails on the Xiaomi Watch 2, follow these steps:
1. Please disable continuous heart rate monitoring in the watch settings;
2. Use the watch to manually measure your heart rate. Ensure the heart rate sensor light at the bottom of the watch is illuminated during the measurement;
3. If the sensor light doesn't illuminate, try unbinding and then re-binding the watch to your device. Alternatively, restart the watch to see if this resolves the issue.
If the problem persists despite these steps, consider submitting feedback for further assistance or testing.