Upgraded from CS 6 to CC 2014 with CS4 Extension

I recently upgraded from Adobe CS6 to CC 2014. I had a custom DW CS4 extension installed and working in CS6. When I converted the mxp file to a zxp file, and then attempted to install the zxp file to CC 2014, I received an error message stating "THe extension can not be installed, it requires Dreamweaver version CS4 or greater." I obviously have CS4 or greater. Any ideas on how to fix this?

Thanks

Mark