MacBook not syncing contacts with iCloud

Hi everyone!

If you have an answer to this issue, your help is greatly appreciated.

Essentially, my MacBook has not been syncing contacts to iCloud. By that, I mean that it has not been fetching nor uploading contacts from/to the cloud. Whenever I create a new contact or update a contact on my iPhone, this information is pushed to the cloud (in fact, it shows up on iCloud.com and on my iPad), but it does not show up on my MacBook. When I use the messages app, for instance, threads with these new contacts show as unknown numbers.

Viceversa, when I create a new contact on my MacBook, this is not pushed to iCloud and does not show up anywhere but on the MacBook. A couple of times it did occur that the contact was uploaded to iCloud, so iCloud.com and my other devices would show two copies of the new contact, but the MacBook would still only show the one.

I have tried disabling contacts in System Preferences > iCloud, restarting the MacBook, and re-enabling contacts. I have tried toggling the fetching frequency in Contacts preferences... The same, un-updated list of contacts appears on the MacBook, without fetching the new ones.

Please let mw know if you have any suggestions or any fixes that don't involve getting rid of all my contacts. My MacBook is running macOS High Sierra (10.13.4).

Alessio 🎈