BLF and Call Pickup

[fra81ita]

Hi,
I'm using some Yealink phones (T32G, T20, T28P and T38G) as testing base for our customers requests and demos.
I'm trying to implement the BLF with "Direct Call Pickup" on Yealink phones.
I've configured the phone as written on some forums and guides, but it won't work.
I can see the light blinking when the phone is ringing, but if I try to pickup the call I receive on "Declined" on the phone

The feature code is working if I use "Direct Pickup" as DSS Key Type and if i dial it from the phone.

Looking at the Asterisk log (live with asterisk -r(and some vvvv) ), I can't see any "activity" sent from the phone, it's shown only the notify of the state from idle to InUse and back to idle.

If I enable "Visual Alert for BLF Pickup" pick it up from the screen is working, but from the button I receive only declined.

I did all the test with three phones (T32G, T20 and T28P). The T38G is in use from a colleague.

Our configuration is:

Asterisk 11.5.0 (provided with Elastix 2.4.0)

T32G
Firmware Version 32.70.0.130
Hardware Version 22.1.2.32.0.0.0
T20
Versione Firmware 9.70.0.130
Versione Hardware 7.0.1.61
T28P
Firmware Version 2.71.0.140
Hardware Version 1.0.0.53

Three extensions in the same callgroup and pickup group

Attached you can find some print screen.

Could you help me to find out the problem?

Thank you very much in advance
Francesco Capuano