When calls are routed directly to a ring group then, my caller ID prefix on that ring group does not work unless those calls are first routed to a different ring group.
Example… At first I had my inbound route go to time of day and then into the ring group but the ring group caller ID prefix would not show up on the phones. So I made a dummy ring group and routed the calls there first, and then to the real ring group when no one answered on the first ring group. Then the caller ID prefix worked great.
I’m running the latest FreePBX on Asterisk 1.4.22-3 & CentOS