Have you followed the tutorial? Did you register the correct flags according to this?
Best posts made by Emil
RE: Is there any support for this product!
Hi. This forum is meant to be a community forum rather than a support forum. For support you should send an email to firstname.lastname@example.org. For your Samsung phone, you could try reboot it in case Bluetooth has hung or similar.
RE: Nokia 8 Android 9 update none of the buttons connected
@tony Android's Bluetooth team messed up the update to Android 9. The cached GATT db structure is erased for bonded devices after the update, so the API gives an empty list of GATT services, making it impossible to communicate with the GATT characteristics. The only way to make it work again seems to be to unbond the Bluetooth device from the system and then bond again.