AVAYA IPO 500 V2 R9 with embedded voicemail. voicemail works for internal calls, but not external calls.

Set up group 501 as night mode, voicemail is turn on. when you ring the main number, it rings and voicemail answers the call, asks to leave a message. After you leave a message, nothing shows up in the voicemail of 501.

But when you ring 501 directly from internal, it has the exactly same procedure. After you leave a message, a new message in VM 501.

Voicemail type: embedded voicemail
Voicemail mode: ip office mode
voicemail code complexity: off
group 501: ring mode: sequential, queuing: on, overflow: off, fallback: off, voicemail: on, voicemail answer time: 5 seconds.

Tried to set voicemail email up, but it did not work either.

Any ideas?