I can create or modify appointments on any of the three devices. Those appointments will not appear in my Apple Calendar app on either of the other two devices. I suspect it is a password issue, but I don't know which passwords to modify.
If you are logged on the three devices with the same iCloud Apple ID then it's not a password issue.
Check in Settings (or system Settings) on all devices, your ID with your photo, iCloud. Make sure that on all three devices Calendar is set to use iCloud, click Display All to reveal Calendar under the first four apps. You may also want to go into Calendar's settings and make sure your iCloud account is activated for use.
If you are logged on the three devices with the same iCloud Apple ID then it's not a password issue.
Check in Settings (or system Settings) on all devices, your ID with your photo, iCloud. Make sure that on all three devices Calendar is set to use iCloud, click Display All to reveal Calendar under the first four apps. You may also want to go into Calendar's settings and make sure your iCloud account is activated for use.
iPhone wont synchronize with Mac and iPad
