Android BLE API: GATT Notification not received

Question

Device used for testing: Nexus 4, Android 4.3

Connection is working fine but the onCharacteristicChangedMethod of my callback is never called. However I

Answer 1

I had another reason that I would like to add as it drove me crazy the whole day:

On my Samsung Note 3 I did not receive notifications of changed values while the same code worked on any other device I tested with.

Rebooting the device solved all the problems. Obvious, but when you are in the problem, you forget to think of.