Regards support site of pebble
FE504502, FE504503, OR FE504504
These error code indicate issues which can often be resolved by restarting the watch from recovery mode.To resolve the issue, please follow these steps:
Your watch may already be in Recovery Mode (pictured on right); if not, please press and hold the back, up, and select buttons at the same time.
Continue holding until your watch screen shows a screen similar to the one pictured here.
Open the Settings menu on your phone
Open Bluetooth under Settings and find any Pebble devices
Tap the icon to the right of the Pebble device(s) and forget them
Reopen your Pebble App and follow the prompts to reconnect your watch to your phone