Thanks for the reply. Here are the answers:
1. When I open Photos on my Mac, "Photos" is selected in the sidebar so all photos are shown, listed in date order, the newest at the bottom of the main window. There it shows the number of photos and videos synced to the Mac, and below that it says "Updating..." but never really updates.
2. iCloud Photo Library and iCloud Photo Sharing are checked, iCloud Photo Stream is unchecked.
3. Importing has "Copy items to the Photos Library" checked.
4. iCloud Photo Library is checked with "Download Originals to this Mac" selected. My Photo Stream is unchecked and iCloud Photo Sharing is checked. (These settings are identical to what is set in the iCloud system preferences Options section)
5. Disk Utility reports no issues. I have DiskWarrior and can run that as well if you think I need to.
6. I currently have 156GB+ free on my 2TB hard drive. Not as much as I'd like, but I can offload and delete some files if that's the issue.
I'm guessing the problem is with not having the My Photo Stream option checked? Funny thing is, this has been working just fine until recently and I haven't changed that setting, it's been unchecked for well over a year.
