likely reasons:

• It won't work if the person viewing the page doesn't have the font installed. To work around that, you can use a @font-face query or a @import query (as generated by fonts.google.com) to import a font from another website.
• Make sure you are applying it to the right element(s) (html or body, and you may need to set it for input and button separately), and using the correct syntax (font-family: "Font 1", font2)