Okay, first off let's make sure that iCloud is turned on in each device AND it must be using the same Apple ID.
On your MacBook Pro;
Click the Apple logo in the top left of the menu bar and chose "System Preferences".
Click the iCloud icon.
Make sure you are signed in and all services have a check mark. Click Account Details and it will list your Apple ID.
If you are not signed in (or the account Apple ID is not the same as you are using on the mobile devices, sign out) then sign in with your existing account.
On your iPhone/iPad
Verify the same Account Apple ID is listed here as is used on the iMac.
Make sure all services are turned on.
Then, restart all devices/Macs.
If syncing still does not occur; Sign into iCloud dashboard: https://www.icloud.com/
Is your content (Contacts, Calendars, etc...) syncing there?If you continue to have questions on this topic, just reply back to this discussion. I will be more than happy to work with you further. Hopefully, this info will answer your question
. If so please, please remember that when you are asked to give a rating, you are rating my personal service only and not this website itself or your issue.
Thanks and good luck,