One of the options that we have available in macOS and the rest of iOS and iPadOS devices, is to synchronize contacts, calendars or reminders in iCloud. This timing may work perfectly for you but it is possible that sometimes it fails or directly that these do not synchronize automatically so let's see a solution for it.
The first thing we have to do before getting into the matter or touching anything in the configuration is to check that the contacts, calendars and reminders are available in the cloud and for this we can directly access the status web of Apple's cloud. We can do it from this same link for see if the system is down or everything is working properly.
In the case of reminders, keep in mind that sometimes they are not compatible with previous versions from macOS and iOS, so you may have problems accessing them until you update your systems to the latest version available.
Backup all data before anything else
Obviously we are going to touch the settings of this data so the most important thing is to make a backup copy of this data on our Mac to avoid possible problems in case of failure. This is essential in everything that requires touching configuration data and the cloud, so remember to make a copy of this data.
Now if we have problems with the synchronization of this data we can start with the simple and it is as we said before, check that we do not have a pending system update. If this is up to date, a series of system requirements must be met to be able to share them and between them:
- Be on iOS 13 or iPadOS
- iWork for iOS (Pages 2.5 or later, Numbers 2.5 or later, Keynote 2.5 or later)
- macOS Catalina
- Safari 9.1 or later, Firefox 45 or later, Google Chrome 54 or later, or Opera
- iWork for Mac (Pages 5.5 or later, Numbers 3.5 or later, Keynote 6.5 or later
- watchOS 6
Now we can continue with the rest of the steps and one of them is to click on the Mac that our iCloud session is active and that we have the same Apple ID on the Mac, iPhone, etc. We access the Apple menu > System Preferences, click on the Apple ID and then on iCloud. If you're using macOS Mojave or earlier, choose Apple menu> System Preferences, then click iCloud. In this sense everything should work.
Usually the service works well but it is possible that for some reason it fails, remember to check the status of the service first and if everything is correct you can follow the steps to try to activate this synchronization between teams of your contacts, calendars and reminders.