I can't export videos to my desktop from Photos (using iPhone X)

I shot a bunch of 4k videos, varying lengths, and now, when I try to move them from the Photos app (using iCloud Photo Library), I get an error like the attached image, and I also have gotten an error when I try to play it in Photos that it's an unsupported file format. That last part I don't understand at all considering I'm using an iPhone and a Mac.

I need to upload these files to my Drive, but they're taking forever from my phone and I'd like to just leave my laptop running to upload them. Need to figure out how I can move them from Photos to my desktop without getting the error message, and what I need to do to get to that point.

Other important info: The movie files are .MOV files, but again, don't understand how it's not supported when they were shot on an iPhone. Using a Mac 2015 with MacOS High Sierra 10.13.1