I'm trying to setup the same, but I cant get it to work.I have the same vto setup. I was able to add a sip phone (Linphone) on my desktop with these settings. Works great.
View attachment 84703
When it request the username/password, I just put:
Username: 9901#0
Password: 123456 (which is the default)
Note in the SIP Address above: sip:9901%230@192.168.1.210 the %23 is a URL encoded #.
Can you please provide the screenshot of you VTO Networking Settings / SIP server.