Is this a google voice problem? 請大俠看一下

Just got ATA box and start to set it up today.

The following is the problem,

ATA spa1001
Line 1. use GV-Sipgate-SS

initially, it works both inbound and outbound. But after a few hours later.

Outbound call is still normal
Inbound call have a problems.

When I call the GV number using another phone.

You can hear the ring tone several times and then appear one voicemail. The voicemail will say "The Google Voice subscriber you called is not available". But the ATA phone does not ring at all.

Anyone experience same problem? Any fix for that?

Thanks a lot.