Re: Strange Uconnect problem
And...WaltA...progressive wasn't actually my problem, but you are correct that that matters.
Here's what I thought mattered:
Location of the file (root of the drive)
Here's what UConnect Support told me that mattered
Thumb Drive Size (MUST be between 4GB and 32GB only)
Here's what I found that *really* matters:
USB size didn't matter for me, I can use both 64GB or 2GB (both outside of the limits given to me by UConnect) with the same result (positive or negative)
Resolution and file size don't seem to be as important as I thought, although there may be some limitations I haven't tested...but I put pretty large and oddly shaped photos up just fine.
I was successful adding photos from a folder, or straight from the root. That doesn't seem to matter.
I did NOT have to have MP3 files on the drive (I read that some people thought that was required.)
I basically found two independent circumstances that would fail - in different ways.
First, if you aren't able to "see" the pictures in the thumbnail view on Uconnect when you are trying to add them from the thumb drive, it is likely that "progressive" setting was used for the image. I didn't originally have this issue, but tested it after WaltA's comment. Gimp, for example, defaults to "progressive" images for jpg, and you have to go into the "Advanced Options" part of the export dialog box to uncheck. That should help some people who can't even "see" the pictures on Uconnect.
Second, if you can "see" the pictures, but get an error importing them, then check for embedded color profiles. This was my problem. I have some advanced color profile settings in Photoshop that get embedded in my images. I have NEVER, and I repeat NEVER, had a problem with compatibility using my color profile (sRGB IEC61966-2.1) with any computer, upload, or device. Until now. When I take the same picture and just change the color profile to a standard sRGB profile (the non-International sRGB), the pictures import just fine in Uconnect. This explains why my problem is unique...most are probably not using photo tools that embed this profile into the images.
So there you have it.... two solutions to two very different problems. And several "factors" that turned out to be a non-issue (at least for me). Hopefully this will help someone in the future who is banging their head against the dash because their imports keep failing.
Thanks for all of the ideas and help.