If you're having trouble with the vibration feature on your Pebbles, follow these troubleshooting steps:

1. Confirm the start of the session in the app: Open the Glimpse app and make sure you've started a breathing session correctly. The app interface must indicate that a session is active. Make sure the app is running on your phone during your session.
2. Check the vibration intensity setting: In the Glimp app, you can adjust the intensity of the Pebbles by tapping the Bluetooth button on the home screen. Find the”Intensity of pebbles” option and adjust it until you're happy with the vibrations.
3. Relaunch the app and Pebbles: Close and reopen the Glimp app. Also, shake the Pebbles to 'wake' them up again and see if the problem persists.
4. Check battery level: Make sure the Pebbles are sufficiently charged. A low battery may affect functionality.
5. Check if a firmware update is required: Open the Glimpse app and check for notifications about firmware updates. If yes, follow the instructions to update the Pebbles firmware and restart the Pebbles and app. Keeping the Pebbles firmware up to date is crucial for optimal performance. Outdated firmware can lead to functional irregularities, including vibration issues.

If the problem persists, please contact Glimp Customer Service for further assistance. We can provide more in-depth troubleshooting or advice on the next steps, possibly including a warranty claim if necessary.