Page numbering in footer Locked?

[Yolstar]

Can I just start by saying, I'm going to rip my hair out!!!!!!!!!
Have a massive document with multiple footers (heaps of section breaks), but one seems to have a lock on it. when i select the document page number, the little button that usually is active that allows me to 'format page number' is greyed out.

Someone on a PC had done some editing on this document, could this be the problem?

How do I get around it. Desperately need an answer ASAP. Thanking you in advance

 

[Yolstar]

WooHoo, all's well and my hair is safe for another day.
For anyone who reads this thread, my answer lay in doing a print preview. The document had many links that it couldn't find. Forcing the document to 'print preview' without the linked documents, seemed to fix the footer problem.

This will probably make absolutely no sense to anyone but me, but there you go!