Many iCal users reported an issue and they have come across an error message saying that the calendar couldn’t be refreshed. Even if you delete and re-add Google calendar, the issue is not resolved. You may notice that iCal calendar didn’t show any updates and in some cases, you may see a message stating that the Calendar is updating. Here are some methods that you can try to get the issue resolved.
Go to Preferences, then to Account and unmark the option that says “Enable this account”. Then you can mark it again. This has solved the issue for many iCal users and they haven’t come across the error message again.
Clear the cache. Delete and add again your Google account.
Another option that you can try is to remove delegates in iCal. To do this, you can go to https://www.google.com/calendar/syncselect and then select all calendars and delete delegates in iCal.
2. Choose the calendars that you want to sync and select the “Save” option
3. Open the Calendar app and press Command_R to refresh & sync calendars
Instead of using the Google account type, use CalDav and then use the full Gmail address and your password. You can also use www.google.com as a web server.