BLF to monitor multiple extensions

I am trying to set up BLF on Grandstream GXP2100 to monitor multiple extensions. Very similar to what was asked here (before the conversation switched to a different topic):

Let’s say, I have extensions 201, 202, and 203 that I want to monitor. I added the following line in extensions_custom.conf in [from-internal-custom] section:
exten => 222,hint,SIP/201&SIP/202&SIP/203

(where 222 is a non-existent extension). Then on the phone I set BLF to monitor 222. Unfortunately, the light is just green.

I also tried exten => 201… (that is, one of existing extensions) in extensions file and on the phone. Same thing.

If I put real extension into the phone (say, 202) and use this extension - everything works fine, light turns red. And dialplan reload does execute - for testing purposes I make other small changes in the file, and the changes take effect.

Anything else I am missing? I played a little bit with configuration files - but it was 2 or 3 years ago. Since then I was fine just using GUI - so I may be missing something obvious…

I just did some testing using Asterisk 11 and FreePBX 2.11. I can confirm that adding your hint line above to the [from-internal-custom] section of extensions_custom.conf works for me. Once you have the line added to extensions_custom.conf, at the Asterisk CLI issue the command:
dialplan reload
core show hint 222
There are two bits of useful output here, the ‘state’ and the number of ‘watchers’. You can see the hint state change from “Idle” to “In Use” whenever any of extensions 201, 202 or 203 are in use. You should also see 1 watcher if your phone has been configured with a BLF to monitor this hint. I know from my experience with certain Aastra firmwares that the phone sometimes does not immediately start watching a hint until some time elapses or until it gets restarted. That is something you can check.

@lgaetz - as always, your response is so clear and to the point! It looks like the only reliable way to get 222 engaged is to reboot the phone. The “real” extensions kick in somewhat unpredictably; but I wasn’t able to engage the “virtual” on this phone.
Obviously, once I know to reboot the phone - it’s not a big deal.

Thanks again!