file format is not supported by photos

We are using iphone x ios 12.0.1 and Mac High Sierra 10.13.6

I am unable to download photos from my phone to my computer library using any software. Bridge, Image Capture and Photos do not "see" or show photos able to be downloaded on this iphone despite their being several hundred from our recent vacation. When using the "Photos" app, i get an error indicating that

"these items cannot be imported to your library because the file format is not supported by photos".

I suspect there are a couple of photos taken with a different photo app that are different, or corrupt or something, but how do I isolate these to allow me to download the rest of my photos? The error doesn't help me identify which files are not the right format, and I can't browse any photos to download. OR, the new modern photos my iphone x is taking are not compatible with my operating system and photos needs to be updated.

What's the deal? How can I fix this?

Many thanks for your help!

Kate