Moved the adapter to a connection to a switch directly attached to the router, and that solved the problem.

My Netgear router would only do port forwarding within the dchp range of the router, and would not allow an assignment to an address outside that range. After completing the port forward configuration and re-booting both the Grandstream and the Netgear, I could ping the adapter and get a response, but could not dial out or into the adapter. Got a fast busy signal.

I even tried to put the adapter in front of the router, and that would not work either. The voip phone service worked, but I could never get an internet connection through the router. I think the same thing happened when I tried to use this method two years ago when I got VOIPO service initially.

So I was relegated to putting the adapter behind the router, and not doing any port forwarding, and that worked fine. That is the way I had been set up before I changed providers and had to put the router in another room where a wired Ethernet connection was not possible, and I had to use a Zytel powerline adapter.

The Zytel works fine for streaming video, but apparently not for VOIP phone service as I started experiencing the audio drop outs during phone calls. Taking the powerline connection out of the equation solved the drop out problem.