Photos not downloading to my Mac

We don't give us much information. I wonder why it's not syncing? Can you tell us

• Are you synchronizing Photos with an iPhone, as well?
• Do you have "Optimized Storage" turned on in Settings>Photos for the phone?
• Do you have "Optimized Storage" turned on for the Mac?
• Do you have at least 10% free storage at on your Mac, on your iPhone, and at iCloud.com?
• On the phone, at Settings>General>iPhone Storage, what does it say? For instance, mine says 76.64 GB of 128 GB used.
• At Settings>Apple ID>iCloud, what does iCloud storage say? mine says 110 GB of 200 GB used.
• What does your Mac's storage indicate?
• At Settings>Apple ID>iCloud>iCloud Drive, is Sync this on?
• On the Mac, have you tried tapping "Sync Now" at the bottom of the Library?

What happens if you

• Restart the computer (of course)
• Re-start in Safe Mode. This bypasses certain potentially disruptive processes, and it often helps. Safe Mode is different for different computers, so see this: 

           Start up your Mac in safe mode - Apple Support