HT503 VOIP Disaster

I"m trying to work with a GRANDSTREAM HT503 to do some voip.
I’ve followed a suggested setup, but I keep getting the FXO busy signal on the grandstream device.
I don’t know what I’m missing. Any ideas?

There are a lot of links in the chain needed to get the HT503 running. Once I was trouble shooting a set up and I swear everything was set up correctly. I called the company administrator for the phone system who was able to access a log file on there end. The company phone system was configured to append the area code to the number the HT503 was dialing out resulting in two area codes because Ignition was also sending the area code as well. The HT503 is not going to tell you these sorts of things and you may need to branch out into troubleshooting in other systems.