Recently we migrated the customer from 8.5 CUCM to 10.5 CUCM. After the migration we are observing that the caller id is not being displayed when the call comes from pstn >> to IP phone >> and picked via call pickup group.
Configuration wise it see...
1. complete call flow
pstn --> gateway --> Ipphone --> call picked by pressing call pick group or by clicking on the BLF.
2. What kind of IP Phones you are using and their firmware?
Cisco IP phone 7975 cmterm-7975-sccp.9-4-2ES13-rel.k3.cop.sgn