I've decided to share my experience with getting the Busy Lamp Field (BFL) list to show on a VVX410 / VVX411 handsets and the expansion module since I can't find this issue documented anywhere and it is extremely difficult to debug. Hopefully it will save someone some time.
This might affect more Polycom models in VVX400 series
I've had a BFL list of 40+ configured on the server but these would never show on the device.
Most often it will only show one single BFL after that line was manually dialed.
This was extremely frustrating as it was rendering the expansion module useless and the service provider would refuse to offer support blaming this on a network configuration.
By chance I discovered that the handset will consistently display all BFLs correctly only if connected to a specific wall socket in the building. No other wall socket would work.
Furthermore, it will not work if directly conencted to the exact same port on the network switch.
It turned out two wires came loose and became disconnected at the back of the wall socket (pin 4 and 5 – blue and blue/white wires in the left side port in the attached picture) and this was triggering something on the handset to correctly display the BFL list on the main unit and expansion module.
After further testing it seems it is sufficient to disconnect only one of the two wires, either pin 4 or 5, and restart the handset. BFL will then work ok and no other functions of the phone are affected.
Weirdly, if I would disconnect the two wires while the phone is on, it would do a short ring/sound alert and briefly display "Network is down" in the status bar, though everything would work fine including in/out calls. BFL list will become populated after a restart.
Reconnecting the wires while the phone was on did not break the BFL list and it could still be used and live updated via the portal. It will however break again after a restart.
I wish this was properly documented or someone could explain to me why this is happening. It makes no sense to me...
Additional info about my config:
Phone Information Phone Model VVX 411 Part Number 3111-48450-001 Rev:A UC Software Version 220.127.116.1181 Updater Version 18.104.22.16898
Power: Power over Ethernet
Network switch: Aruba 2530 48G
Cabling: Cat6 Ethernet
That is a strange situation/fix; I would have initially leaned towards network and/or transport protocol.
As far as I know, 4,5,7,8 are used for PoE with two of ea in parallel to create positive and negative and allowing for the most possible copper to be used for power.
Ititially I was a little concerned for you in losing 1/2 of the power capacity of the run, but according to Polycom power usage stats Here, a 410 with a single sidecar should draw at max 7.2W .. doing our math on 48v PoE that's .15a; 24AWG can carry a max of .57a, and 23 can handle up to .72a, so I guess you'll be ok missing the extra copper.
Still strange. I'm glad you got it going.