Ical error message "your calendar couldn't be refreshed" make sure you're connected to the internet and try again

Question

I've noticed on my Macbook Pro (10.9.3) iCal, iCloud section on left showing error icon after syncing (circling motion to indicate it) ends. When I click the icon, message "your calendar couldn't be refreshed. Make sure you're connected to the internet and then try again later" comes up even though it is connected. iCal no longer syncs with iCloud Calendar ether.
Could someone know what my problem is here?
I have no issue with Contacts or Mail. They just sync as usual.
I have checked my iCloud account and it is correctly set up.
Please help...

Answer 1

Hello there, RS.7.
The following Knowledge Base article offers up some great, in-depth steps for troubleshooting issues with iCloud Calendar on your Mac:
iCloud: Troubleshooting iCloud Calendar
http://support.apple.com/kb/TS3999
Particularly:
Troubleshooting on OS X
Server error 507?
If you're using OS X Mountain Lion or OS X Lion and get the message “The server responded with ‘507’ to operation CalDAVWriteEntityQueueableOperation,” you've exceeded one or more iCloud Calendar limits. Try removing some calendar or reminder data from your iCloud account.
Confirm that you've turned on iCloud Calendar:
Choose System Preferences from the Apple menu (), then click iCloud.
If you're using OS X Mavericks v10.9 or later, make sure that the Calendars checkbox is selected.
If you're using OS X Mountain Lion or Lion, make sure that the Calendars & Reminders checkbox is selected.
Try each of these steps, testing after each to see if the issue is resolved:
Make sure that you are using OS X Lion v10.7.5 or later. Learn how to verify the version of OS X you are using.
Make sure your computer is online. Attempt to view www.apple.com. If you can't connect to the Internet, your iCloud calendars and events will not update in Calendar or iCal. Learn how to troubleshoot your Internet connection.
Open a secure website to test if ports 80 and 443 are accessible. Calendar requires port 443 access to iCloud in order to push and fetch updates to and from the iCloud Calendar servers.
Choose Apple () menu > System Preferences, then click the icon for iCloud. Make sure that you're signed in to the same iCloud account that you're using on your other supported devices.
Make sure that you enter and update calendar information in the iCloud section of Calendar or iCal. Only calendars and events in the iCloud section of the Calendar or iCal Calendar list are updated in iCloud. Both Calendar and iCal for Mac support the display of and interaction with multiple accounts and datastores, such as iCloud, On My Mac, Exchange, and Google. This makes it easy to create or modify events or calendars in a section of Calendar or iCal that may not be updating iCloud. Learn more about moving local calendars to iCloud.
In some cases, you may find that you have data duplicated in both the local On My Mac and the iCloud sections of Calendar or iCal. Learn more about resolving this issue.
You can make the iCloud calendar your default calendar for all new events. In Calendar, choose Calendar > Preferences, then click General. In iCal, choose iCal > Preferences, then click General. Locate the Default Calendar setting and choose one of the Calendars under the iCloud heading. Close the Preferences window to save the change.
If recent changes don't appear, try forcing Calendar to refresh by selecting Refresh Calendars from the View menu. In iCal, select Refresh or Refresh All from the Calendar menu.
If you've recently made changes to your contacts' birthdays and are not seeing those changes reflected in your Birthdays Calendar, try to refresh your calendars. If you made the changes in the Contacts app on an iOS device or at iCloud.com, it may take up to an hour for those changes to appear on your other devices. 
Make sure that your account was successfully created in Calendar (or iCal) on your Mac. After upgrading to iCloud Calendar, you may need to quit and reopen Calendar (or iCal). To confirm that your account is configured correctly in Calendar (or iCal):
Open Calendar (or iCal).
Open Calendar (or iCal) Preferences.
Click Accounts. You should see an account with your iCloud member name in the Apple ID field.
Turn iCloud Calendars off and back on:
Quit Calendar (or iCal).
Choose Apple () menu > System Preferences, then select iCloud.
Deselect the checkbox next to Calendars (or Calendars & Reminders in Mountain Lion and Lion).
Close System Preferences and wait about a minute.
Open System Preferences and select iCloud.
Replace the checkmark next to Calendars (or Calendars & Reminders in Mountain Lion and Lion).
Close System Preferences.
Open Calendar (or iCal) and test to see if the issue is resolved.
Restart your computer. This may sound simple, but it reinitializes your network and application settings and can frequently resolve issues.
Thanks for reaching out to Apple Support Communities.
Cheers,
Pedro.