1. Watch battery is low: low battery power may cause backlight failure. You can try charging or replacing the battery.
2. The watch system setting is incorrect: You can enter the system setting on the watch to check whether the backlight setting is correct. If the backlight is set to "always on" but the watch is still not on, you may need to contact after-sales service or professional maintenance personnel for inspection and maintenance.
3. Watch screen failure: If the watch screen fails, such as unable to display content or color distortion, the backlight may also be affected. In this case, you need to contact after-sales service or professional maintenance personnel for inspection and maintenance.
The above information is for reference only. If you can't solve it, you can check the professional technical documents or consult after-sales service.