Problems porting an existing VOIP phone number to Digital Voice

Has anyone been able to successfully port an existing phone number from a VOIP provider to Verizon Fios Digital Voice?  

I've been trying for 2 weeks with no luck.  The last Verizon support person told me that it's impossible to port from VOIP to a landline.  He seemed confused when I told him that I thought the Digital Voice product was not a traditional landline.  Also, my Voip provider told me they have ported several other numbers out to Verizon without a problem.

I've had this phone number for about 10 years so I'd really like to keep it.  It was originally owned by Verizon but I ported it to Cox Cable several years ago.  It was ported again to my existing voip provider approx 1.5 years ago.  

We also moved to a new address this year so maybe that is causing a problem.  I read somewhere that the porting process depends on both the phone number and address.  We're in the same town but probably a different billing center.  Has anyone run into this problem?

I'd appreciate any advice that people may have from their porting experiences.