Photos on MacBook has stopped updating?

About the status bar in Photos for macOS - Apple Support

I have a MacBook Pro, up-to-date IOS.

Do you mean "up-to-date MacOS X"? iOs is the system for for iPhone or iPad. The most current version of MacOS X would be macOS 1014.3 Mojave, but your signature is showing 10.13, that would be High Sierra.

If Photos cannot update the library , there may be there possible problems.

1. Are you perhaps running out of iCloud Storage? Then the updating will stop. Or is there problem with your AppleID? Check into your iCloud account in System preferences > iCloud, and check, if you need to update your payment information, for example the expiration date of your credit card.
2. Photos may not be updating, if you are having items in your Photos Library, that cannot upload to iCloud. Have you checked the status as described here? About the status bar in Photos for macOS - Apple Support. Create the two smart albums mentioned in the document. Are these smart albums empty?
3. You may have a network problem. The updating will stop, if Photos cannot access Apple's servers. This can happen, even if all other network services are working fine. Are you using third-party security software? A Firewall or Antivirus software, like Kaperki? If yes, disable them and restart the Mac. Does the iCloud syncing resume? And how are you connecting to the internet? iCloud Photos needs a Wi-Fi connection to sync on High Sierra. A cellular Hotspot will not suffice.