Step two is to ensure you are logged into iCloud using the same Apple ID on all your devices. Go to icloud.com, login with your Apple ID and then tap iCloud Settings (either the gear-shaped box icon or by selecting it in the drop-down menu underneath your name at the top right of the iCloud browser window).
If you regularly experience sync problems with your iOS device(s) and you know your network is stable, then you should try logging out of your iCloud account on your iOS device or Mac, then log back in.
If problems persist then close and restart the relevant iCloud-enabled app: Contacts or Calendar, for example. Double-click the Home button (or swipe up to about halfway up the screen and hold for a second or so on iPhone X), swipe through your active apps and swipe up to close the app. (You can long press the app icon and then tap the X that appears on iPhone X.) Return to the Home screen and wait a few moments before launching the app again.
Another approach that sometimes works is to turn off iCloud Contacts and turn it on again. Go to Settings>Apple ID>iCloud, then turn off Contacts. Unless you have a copy of your contacts stored elsewhere, you should then choose Keep on My iPhone/iPad.
Never underestimate the power of a hard reset to resolve many iOS problems. To achieve a hard reset on iOS devices simply hold down the Power and Home buttons until the device turns off and the Apple logo appears. The device will restart and system processes will be refreshed, which sometimes fixes iCloud sync problems.
Hello, and thanks for dropping in. I'm pleased to meet you. I'm Jonny Evans, and I've been writing (mainly about Apple) since 1999. These days I write my daily AppleHolic blog at Computerworld.com, where I explore Apple's growing identity in the enterprise. You can also keep up with my work at AppleMust, and follow me on Mastodon, LinkedIn and (maybe) Twitter.
d3342ee215