EMP BLF fail for snom 720 (Agent Login/ Logout to all Queues)

I’m trying to configure a BLF with my SNOM 720 phones
when configuring a key and choosing BLF the light turns on and off if I manually dial the code to login or logout
e.g. for ext 412 : 45412
when configuring via EPM I and clicking the blf I get “Declined” on the monitor
when browsing to the phone to see the key’s current value I see :
sip:45[email protected];
if I click apply, snom’s config automtically changes the key’s value to :
a value that actually works fine with the blf.

Any help is much appreciated.