Verify if all your calendars are marked to be visible by pressing toolbar button Calendars and you are saving event to proper calendar.
Your calendar is synchronized from one device to another using a cloud calendar.
To identify which device fails to synchronize please follow these steps.
- Enter a new event in device A
- Login to your cloud calendar (B)
https://www.google.com/calendar (see Sync with Google Calendar / Sync All Calendars if only one calendar is syncing)
and check if the event you just created is there.
- If not, then the sync problem is between device A and your cloud calendar (B)
If the event is there it means there's a sync issue between your cloud calendar (B) and device C
In 90% of cases the procedure below solves the issue.
We use iOS' native synchronization functionality, so this is a general iOS problem, not caused by our app.
On your iOS device:
- Backup your colors if you are using custom colors ( App Settings > General > Synchronize colors )
- Go to System Settings
- Go to Accounts & Passwords (Calendars in iOS10 or Mail, Contacts, Calendars in iOS9 and below)
- In the Accounts section select the calendar having a problem (iCloud, Exchange, ....)
- Reset / Re-sync the calendar data by toggling CALENDAR setting OFF and ON again
You might need to reboot your iOS device afterwards, forcing it to sync.
Warning: If events are only available on device and are not synced to the cloud, resetting sync will delete the events not synchronized.
For safety you can make a backup of these events using ICS export, see Create ICS File for Export
Should toggling calendar not result in desired sync you can also remove the account, reboot and then add the account again.
If none of the above solutions work for you, please contact your Calendar service provider (iCloud, Google, ...) to resolve the problem.