You can file an appeal within 3 months of the date of denial to the:
Appellate Tax Board (ATB)
100 Cambridge Street Suite 200
Boston, MA 02114
Phone: 617-727-3100
Call the ATB for an application; or use the link to the ATB website. The application is not difficult to complete, and the ATB is more than fair to homeowners. However, your case may not occur for a year or so.