@gjacobse said:
I think you have the Ftype and Assoc backwards.
http://superuser.com/questions/204354/how-do-i-get-ftype-assoc-to-match-windows-explorer
Not unless Microsoft is wrong about there own commands.
https://technet.microsoft.com/en-us/library/bb490912.aspx?f=255&MSPPError=-2147217396