Why is photoshop window cutting off bottom of my file

I have an art watercolor print (18"x24") that I scanned into PhotoShop in July 2014. It was 334M.  I tried to open it in 2021 PS and the file only shows about an inch.  I cannot get the entire image on screen.  It jumps up an down when I try to manipulate it, but does not stay in place and disappears to the top shoping a narrow white ribbon at top.  

I have a fairly new iMac with newest OS (Big Sur) and plenty of memory.  I also attached several scratch discs.  I did this on an older mac using older software.

All I want to do is make some adjustments and send it to an art printer.