Problem printing 4x6 inch print

I’m using a 2021 iMac M1 and am pleased to find Acorn 7, I like the simple interface. I also use Pixelmator Pro and Affinity Photo. With Acorn 7 I am unable to make a 4x6 inch print, although I have no trouble with 5x7 or other sizes. It appears that one must set the type of paper under Page Attributes and then change the paper sizes. The printer interface show the proper size preview image on a 4x6 page, but it prints only a think strip. I resized my image to 5.8 x 3.8 in for these test prints. I am using a Canon Pro-100 and I have installed the driver for the M1 iMac. I have no trouble printing any 4x6 image with Pixelmator Pro or Affinity Photo. thanks, David

If you save your 4x6" image as a PDF, open it in Preview, and then print from there - does it turn out correctly or does preview have the same problem?