The notification LED behavior changed in HTC’s
4.4.2 (KitKat) update.
If you updated your HTC phone to this version, the notification LED will show a flashing green light when there are pending notifications and the display is off.
To check and make sure there's no hardware problem with the notification LED, use the HTC Guide app.
If this app is not preinstalled on your phone, you can download it from
Google Play Store.
Open the HTC Guide app.
Check whether the notification LED alternately flashes green and orange.
If it does, that means the LED is working just fine.
Another way is to use the HTC diagnostics tool which can be accessed through the
Phone app. On the
Phone keypad, enter