Faxing using voip phone service

We have connected a PIXMA MX 700.  Our fax number worked with an old HP 1010 fax, but it is not working with the new machine. We have voip phone service.  If I call our fax number, the fax rings a few times, then screeches briefly, then rings again, screeches briefly, etc.  The message someone gets if they try to fax us is that the fax is not answering.  Is there a setting we are missing?  
Thanks, Merrilee