I did switch to Classic template and that did not resolve the problem. But as it goes, I've given up on trying to use 'Use Proportional Images on Products and Categories' and found another solution.
If I make 3 versions of an image (S, M, and L) and FTP them to the correct directories, then they show up on the site. I was trying to avoid this because I didn't want my client to have to a) create 3 sizes and b) have to FTP stuff, but alas... it seems the only way to work this out and move on.
I thank you for your help. I appreciated your efforts.
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