A family of Microsoft word processing software products for creating web, email, and print documents.
The quickest workaround is to edit the header or footer and insert the page number at the location of the insertion point by pressing Alt+Shift+P.
The page number formats may be missing because of a damaged building blocks template. You can delete it and have Word create a new one, with factory defaults, for you. See https://www.addbalance.com/word/pagenumber10.htm#PageStart .