I cannot add page numbers in Word (no x of y...)

I've seen this happen when Word's Building Blocks or Normal.dotm template becomes corrupted. Try creating a new blank document first to see if the issue is document-specific. If the Page X of Y templates are still missing, run an Online Repair of Microsoft 365, rename Normal.dotm, and reset the Building Blocks folder. As a workaround, you can also manually insert the fields { PAGE } and { NUMPAGES } in the footer to create Page X of Y numbering.