The restore calendar is a different function. Mainly for restoring to a backup if you lose anything. But that may refresh the sync.
If that didn't work, then please do the steps below exactly as this will re-establish the connection with servers
First on your Mac, open Calendars app. Click on File menu and select Export. Then Export the calendar to your Documents folder or any other folder for backup.
Then go to System Preferences > iCloud and click Sign Out. If asked to Keep or Delete stuffs, select Keep. If you only get Delete, then delete it. You will get them after signing back.
Once you are signed out, wait 2 minutes, then go to System Preferences > iCloud and sign in again. (Make sure you sign in to same account you used on your iPhone, in Settings > iCloud)
Then go to System Preferences > Internet Accounts. Select Google account in left column and sign out or delete it. Then add it back again by clicking the + button. This will re-establish the connection with Google servers (if you are syncing with Google as well).
Once you did the above steps, you have to re-estalbish the connection with iPhone as well. For that, on the iPhone, go to Settings > iCloud. Sign out and then sign in back.
BTW take your time and you can ask as many follow up questions you want without any additional charge.