Device not found error message and photo files can't transfer when connecting iPhone 11Pro to Dell XPS15
When I plug in iPhone 11Pro to Dell XPS15 PC, the error message says through auto-pop-up Photos: "We're having trouble connecting. " (Phone is unlocked and open to All Photos.) I have gone through File Explorer and opened each of the phone's DCIM folders: 100Apple (425 files), 100Cloud (7 files), and I have successful dragged and dropped these onto a hard drive.
However, 101Apple has 685 files, but only 645 can be copied/pasted, dragged/dropped.
And on 102Apple folder, the phone shows 516 files, but the backup only shows 122.
All files appear to be on iCloud. However, when I download from iCloud, the images are tiny (500KB rather than 5 MB.
I downloaded iTunes because I was told I could use that to transfer original files, but I have been unable to find instruction on how to use that.
Earlier (like maybe March 2020), I was able to simply plug my phone into my desktop and upload all images from my iPhone full res.
I need them at full res. Initially, I had the phone set to Optimize, and have now set it to Download and Keep Originals.
iCloud is enabled on both laptop and phone.
Still, nothing is working properly and I need help, please.
iPhone 11 Pro, iOS 14