The original sentence is vous parlez le français, but with parler the definite article le isn’t mandatory and it is frequently omitted. If you would like to use française, you’d have to say vous parlez la langue française.

In French what humans use to communicate with their voice is called "une langue" (feminine word) but it is also called "un langage" (masculine synonymous word) and there is no reason why the gender of the name for the language should be aligned on one of the terms rather than on the other. It happens that historical circumstances resulted in the choice of the masculine. This is generalized to all languages.

All names of languages in French are masculine, without exception: (ref.).

• La Pologne, le polonais
• La Russie, le russe
• La Chine, le chinois
• Le Danemark, le danois
• Le Portugal, le protugais
• La Suède, le suédois
• La Finlande, le finnois
• Les Pays-Bas, la Hollande, le hollandais, le néerlandais
• etc.