A single page cannot be aligned vertically in a different fashion (i.e. Center) than surrounding pages without section breaks.
Sections / Headers and Footers in Microsoft Word (Ribbon Versions)

You could post a sample problem document - absent proprietary info and someone here will likely take a look at it.
How to attach a file in this forum.

Keep in mind that Word is really not a page layout program. Publisher is.


How to put a portrait page number on a landscape page by Bill Coan, MVP