The UUID 0x2902 is the complete 16-bit value for that UUID. It is not normally required to supply 128 bits of data to identify a 16-bit UUID. If your APIs do require this for some reason, then the 128-bit format that you specified above (ending in 00805F9B34FB) should work in this case as well. If the process worked for subscribing to notifications on another system, then it should also succeed here as long as you are using the correct attribute handle (0x0012 for the Unack'd Data Client Characteristic Configuration Descriptor).
Thanks for the reply. It is an Android app I am trying to connect to the BLE. I am not very experienced with neither the BLE and Android so it might be my questions are irrelevant.
Anyhow I tried to convert the 16 bit UUID to 128 bit (65332902-A115-11E2-9E9A-0800200CA102) without success though - it is not accepted by the app.
I properly have to do my homework a little bit better :-).
OK - I found it now the UUID to be used for notifications. I downloaded your app "CySmart" from Play - this can show the descriptors. This was very helpfull.