I know there is a similar question but nothing suggested there worked, unfortunately…
I have an iMac (OS v10.13.6) which has the original photos and it syncs flawlessly with an iPhone X, iCloud.com, with iPad mini and, until recently with my MBP (OSv 10.13.6) . The latter, all of a sudden, stopped syncing while the others are in sync!
I have tried:
1. unchecking “iCloud photos” and rechecking.
2. Repaing the photo library
3. Unchecking iCloud photos >> Repair >> Recheck
4. Unchecking iCloud photo >> New library >> Recheck
5. Numerous restarts of the OS in between…
Nothing seems to help!
Thank you in advance!
Here are some solutions found on this Link
1) Check the Internet connection on your devices, As you may know, a
stable network connection on your iOS device and Mac is required to
upload photos to iCloud. Thus, you need to make sure the Wi-Fi network
connection works properly on your Mac and your iPhone (or other iOS
devices). If you find Wi-Fi not working on your devices, learn how to
fix it from the related article.
This is the first solution you should try when iCloud photos do not
sync to Mac or photos are not downloading from iCloud to Mac.
2) Check your Apple ID To sync photos across your Mac and iOS devices,
you have to sign in to iCloud on these devices with the same Apple ID.
When you find iCloud photos not syncing to your Mac, go to check your
Apple ID and see whether it’s the cause of the issue.
3) Turn on iCloud Photo Library and My Photo Stream To access photos
your photos and videos from all your devices, you need to turn on
iCloud Photo Library/My Photo Stream on both your iOS device and
computer. If iCloud photos are not syncing to your Mac, you should
also check whether the options are set up correctly.
On iPhone/iPad: Go to Settings > [your name] > iCloud > Photos and
then switch on iCloud Photo Library and My Photo Stream. On Mac: Go to
System Preferences > iCloud, make sure Photos is selected and click
Options next to it. Then turn on iCloud Photo Library and My Photo
4) Check your iCloud Storage Apple provides 5GB of iCloud space for
free. But 5GB is generally not enough for you to store your iPhone
photos and videos. It’s possible that iCloud Photos Not Syncing to Mac
is due to insufficient storage in iCloud. If that’s the case, you can
either buy more iCloud storage or go to Apple Menu > System
Preferences > iCloud to manage iCloud space on your Mac.
I hope this helped fix your macbook pro.
Source : Link , Question Author : Dimitris Iosif , Answer Author : Sparky