I have a GXP2010 phone and ucm6202
I have problem with blf.
After phone reboot evrything works well, but after some minutes blf are not working.
I have a cisco spa phone and blf works just fine, so the problem is with GXP2010 setup.
In GXP2010 account1 menu i have:
Register Expiration: = 1800
SIP Registration Failure Retry Wait Time: = 20
Session Expiration: = 180
Min-SE: = 90
I can give you more details if you need.