The firmware update via the application can sometimes fail or be blocked at 99%.
If the firmware update does not finish, the toothbrush will be "bricked" (the LED will glow brightly in green). In order to solve this problem, could you please try the following steps:
1 - Forget the toothbrush in the Kolibree application by clicking on the toothbrush icon then click on the name of the brush and finally "Forget this toothbrush".
2 - Kill the application.
3 - Reset the toothbrush by holding the button for 10 seconds (the LED will change color and turn off, it will mean that the brush has been reset).
4 - Empty the cache from the settings of your smartphone.
5 - Restart the application.
6 - Open the settings of the toothbrush.
7 - Select "Add a toothbrush" and try to associate it without a loader.
The toothbrush should pair and restart the firmware update.