Thanks to a forum I found on Kindle Apps, it looks like I'm not the only one with that issue so I thought I would share it here as it seems to be working!
The posted fix is to go to the table of contents menu and select a chapter and it resets the page to that chapter. The page numbering works from then on in that book. I just clicked on Chapter One and it's working properly now. I'll just have to remember to do that with any future book that I have that issue with.
Or write myself a reminder note on my files in case I forget.
