Sadly I have to join this thread. I've had the adapter for a couple of weeks, and used it for outgoing calls with no problems, while the port finished. That happened yesterday, and now that the incoming calls are coming through VOIPo, I am having issues with many callers not being able to hear me. Does not seem to happen with all calls, just some. None of the suggestions in this thread have helped.

Setup is Cable Modem (Comcast) --> Grandstream --> Linksys router

Since I work at home, I need my phone working correctly. I can't believe that I am missing AT&T after just two days.

Opened a ticket, let's see what they say. But as a new customer, I am less than impressed.