Phil, thanks. Using that info I tried a few things and....
I tried copying the sheet block on the main sheet as well as deleting the block and adding it back. Deleting the block requires a redo of any formatting of the block when adding it back. I’m using the blocks to form a diagram, so that is too much work, but it puts the new sheet at the end of the main schematic file and so the last page number. The copying operation also seems to move the copied sheet to the end of the file and so the last page number. This preserves the size and other details, so is easier to do.
However, in the end I just copied the sheets in the main sheet file via text editor. It was just easier. But at least now I know I must have tried copying a block on the main page which mucked the page order.
The delimiters of the sheets are $Sheet and $EndSheet with only four lines between. Not remotely hard to do and it doesn’t require touching every block again if you need to put something near the head of the list.