I have tried setting these up with identical parameters. the SPA525G can make calls, the 8851 cannot. When I place a call, even inside the network to another extension on the same network, it does not go through. When I look at the console, it does not show a call attempt even being made. I have a feeling the call is never leaving the 8851 and making its way to the PBX itself since nothing shows up in the PBX console when I make a call from this phone, but something does show up when I make a call from any other extension.
Is there any strange quirkiness on the 8851 I should be aware of that is not a problem on the older SPA525 series?
I can receive calls from inside or outside the network, I just cannot make them, to outside numbers or internal extensions.
I have went through my settings on older phones and newer ones and am totally stumped. we have grandstream 2160 phones as well as spa525g phones that work without issues on the same network.