To resolve the issue of missing or deleting page numbers from the headers of a document:

1. Locate the Header and Footer view mode by selecting the View tab in the top, ribbon menu bar.
2. Once the header and footer view is enabled, select the box containing the page number.
3. To delete a page number, press the delete key on your keyboard.
4. To insert a page number, select the drop down menu from the Header and Footer tab and select the Page Number option.