Page Numbers in Word 2007-2016
Keep in mind that page numbers are a creature of headers and footers. You need to know where they are and what kinds are there. Every Word Section contains three headers and three footers none of which may be displayed since a page can have multiple sections. Header/Footer Settings Recap

There is a free tool available that can help you figure out where your page numbers are and where the sections are. Word Toolkit for Advanced Management of Word Headers and Footers

Post more about what is going on for actual help. "It isn't working" is not quite specific enough.