Macbook Pro stopped syncing photos to and from iCloud suddenly

Solution 1:

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 Stream.

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.