In my case i made the following mistake in my css code.

    font-family: 'Open Sans', sans-serif !important;

This will override all font family rules for the entire page. My solution was to move the code to body like so.

    font-family: 'Open Sans', sans-serif;

NB: Whenever you use the !important flag in css, any other css rule declared of the same type on the same element will get overriden.