I have an HP 6500 Wireless all in one connected to a Vonage fax line. I had to toggle the fax baud rate to the lower numbers, 9600 or 14400 to get faxes through. Higher baud rates would not work. You should be able to adjust rate starting at 9600 and test at that level, then try at 14400, etc.
Good luck, it can be frustrating
I have checked and re-checked the set up. Fax tests come back "pass"
When I try to send I hear the dial tone,machine dial the number,and the phone ring. After 4 rings I get a busy signal no matter what fax number I try to fax. If I call my fax line from another phone, I hear the computor tones and the phone line is clear of noise or static. I have disconnected every other device(phones,call display, answering machine and still get the busy signal. I have filters on every line except the modem for wireless internet.The fax is set higher than the answering machine ring number. This busy situation occurs wether I try to fax from the HP control panel or through the software. I simply just get confused trying to resolve this with the HP information. Anyone Had a similar problem?