Jody has a Mac and a Samsung Galaxy Android Phone. He used to be able to sync the calendar on both with no problem. But lately, he's been having issues with the built-in Mac calendar and the Android Calendar program. Leo says it's possible that Jody's Calendar hasn't been syncing to iCloud, which is what Apple does before syncing to other devices. Apple may have logged him out before an update. Also, make sure it's not requiring 2-factor authentication now. Look into the iCloud settings and make sure that the Calendar is syncing.
Then, look into the Android device and see where it's getting the data. Leo also recommends moving over to Google Calendar. It will be much more seamless with cross-platform connections.