works by pstn gateway but not direct voxalot

[vientito]

I have a strange problem with a friend. It comes to my attention recently that sometimes her voxalot number could not be reached by my voxalot phone. When I dial the number I hear total silence for about 6-7 secs then the voicemail comes on. During this time of difficulty, I could dial the local PSTN gateway thru sipbroker to ring her phone.

Then a while later, everything goes back to normal. This happens so random that I could not pin down to what exactly is causing this issue.

As far as voxalot goes, her case is the only one I have come across. All the voxalot accounts I have installed are fine and working normally. All except this one.

Any suggestion?