The firmware update via the application may sometimes fail or be blocked at 99%. If the firmware update doesn't complete, the toothbrush will be bricked (the LED will be solid green).
To solve this problem, please follow these steps:
1 - Forget the toothbrush in the Kolibree App and if necessary in the setting of your device
2 - Quit the App
3 - Reset the toothbrush
4 - Relaunch the App
5 - Open the toothbrush settings
6 - Select ‘Add a toothbrush’ and try to pair without a charger.
The toothbrush should pair and restart the firmware update.