Forget the ring group issue for the second.
If an extension is engaged in a call, either in, out or internal to another extension, does the BLF show the extensions to be in a call (solid red)?
If the PBX is setup correctly and sending the NOTIFY messages to the phones, the BLF for an extension will show (*) -
- Green, Idle, available to take a call, pushing the BLF will usually result in a speed-dial to the monitored extension.
- Blinking Red, Ringing, pushing the BLF will usually result in an intercept of the call ringing the monitored extension.
- Solid Red, Actively in a call or DND, pushing the BLF will result in a speed-dial to the phone and depending on the condition, will allow it to ring or follow the busy route set for the monitored extension.
- No indication - the monitored extension is not registered to the SIP server and is off-line. Pushing the BLF will cause the call to follow an unavailable routing set for the monitored extension.
(*) all of the above is somewhat conditional on what the PBX programming is set to do. The phone is only reactive to the NOTIFY message sent by the PBX. When the subscription is active to monitor an extension, the BLF for that extension will always show one of the 4 light patterns mentioned above, but the conditions may be somewhat different. As an example, some systems will show an extension as in a call when the extension is set DND, others will not.
If you have a BLF set, and it is not showing an active call (solid red), then the PBX is not sending a Notify.