During calls with SRTP encryption enabled, all Snom handsets do not show an indicator if the encryption is working successfully.
Even worse, the missleading lock symbol does only symbolize the keylock of the phone keyboard, but not a established encryption.
Do you see the same behavior on your handsets?
please refer to our answer in the other forum entry:
We have already opened a feature request for this request but for the time being we cannot say when this will be implemented. internal reference number: DECT-573!
snom support team