Cannot enter text into headers in Numbers

With a Numbers Spreadsheet, when I chose to print, I should be able to type text in the document header.

I cannot type in the new text.

I can paste the text into the header from somewhere else.

I am using MacOS 12.5.1.

2019 iMac, lots of RAM, disc space...

I have rebooted my computer

I have un-installed Numbers, rebooted, and reinstalled numbers

I have created new documents

The issue continues.

Any solutions?

The only workaround I have found is to click done and go back to the spreadsheet. Type what I need in a blank cell, and cut what I have typed. Click on print, then paste the text into the header.

It works but is a real pain.

Chaz T