Can't download full resolution photos on iphone
My iPhone 6S Plus (fully up to date) just recently started storing only low-res versions of photos I'd taken with it, and I believe that this is because the phone automatically enabled "Optimize iPhone Storage" and uploaded the full-res versions to iCloud. My understanding is that when a low-res photo is viewed on the phone, the full-res version is automatically downloaded, or at least when the photo is selected for editing, this is supposed to happen.
VIDEOS, on the other hand, which appear very coarsely pixelated until ">" is tapped, download and play immediately in full resolution.
I cannot get the full-res versions to display just by viewing photos. When I select the editing icon, I get this message: "There was an error downloading this photo from your iCloud Photo Library. Please try again later." "Later", of course, I still get the same message. Clicking on "Download and Keep Originals" in Settings checks that option and unchecks the "Optimize iPhone Storage" option, but a note appears telling me that "This iPhone is currently storing originals in iCloud, yada yada" and the full-res versions of photos still won't appear no matter what I do. There is nearly 1.6 GB of free space on my iPhone, which is not enough to contain all of my photos in full res (in low res, they occupy some 800 MB), but it's obviously enough to allow for ONE to be downloaded.
What's happening, and how do I fix it? I want my normal beautiful full-res photos HERE on my iPhone!
MacBook Pro (Retina, 13-inch, Late 2012), OS X Yosemite (10.10.1), 500 GB SSD