If offline mode cannot be established, here are several things to check:

  1. Make sure your phone / tablet has a reliable connection to the internet
  2. Make sure that Sentinel App has Bluetooth and location permissions
  3. Make sure you have Bluetooth enabled
  4. Make sure the device is running (LED are blinking) and that the phone is in proximity of the device
  5. Restart sentinel app
  6. Clean up old Boat monitor devices from Paired devices list
  7. Restart your phone


Details:

6. Android phones limit the number of paired devices. This limit is usually 100 devices, but sometimes lower. Each device that you test is added to the list of paired Bluetooth devices. When this list is full, you cannot add more devices, so you have to delete the old ones. Go to Connections/Bluetooth in your Android settings and Forget/Unpair old Boat monitor devices.