ICAL Server Responded With An Error | Steps to Fix

The “iCal server responded with an error” message typically occurs when there is a problem syncing or updating calendar data with an iCal/CalDAV server, especially in macOS or iOS Calendar apps.

This can happen from corrupted events, recurring event issues, or server communication errors.

Common Causes and Fixes

• Corrupted or Conflicting Calendar Events:

  • Sometimes recurring events or events associated with deleted accounts cause sync errors. For instance, a recurring event from a deleted Google account continuing to send requests triggers this error. Fix by logging into your calendar service web interface (Google Calendar, iCloud, etc.) and delete or edit problematic recurring events.

• 400 Error from CalDAV Operation:

  • This indicates a bad request due to calendar data issues. Clearing out problematic events often resolves this.

• Email Provider Changes:

  • Some users experienced this when email providers like Verizon/AOL/Yahoo changed back-end email handling. Switching to “Basic” mail mode in webmail settings restored functionality.

• Sync Issues with iCloud or Third-Party Servers:

  • Try removing and re-adding the calendar account to force a fresh sync.

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Steps to Fix

1. Log into your calendar service (Google Calendar, iCloud, etc.) on the web and check for suspicious or old recurring events, especially from deleted accounts. Delete them if found.

2. On your device, try removing then re-adding the calendar account causing issues.

3. Clear cache or settings related to calendar apps, if possible.

4. For mail providers (AOL/Verizon/Yahoo), switch to “Basic” mail mode on their webmail portal.

5. Restart your device to clear any temporary sync errors.

This should resolve the “iCal server responded with an error” messages related to calendar sync and recurring event conflicts.