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FRITZ!Box reports "Internal system error (17) occurred" when adding a Google calendar

When setting up automatic switching for the smart plug, for example FRITZ!DECT 200 or the LED light FRITZ!DECT 500, you cannot add a Google calendar. During the authentication process, the error message "The authentication process for the Google Calendar could not complete the procedure successfully. Internal system error (17) occurred" is displayed.


  • The calendar was not set up on Google yet or was not set up correctly, or the name of the calendar contains illegal characters, or it is misspelled.

1 Correcting the name of calendar

  1. Sign in to your Google account.
  2. Rename the calendar you want to use for the smart home device: Remove all special characters, spaces, letters with umlauts, or accented letters from the calendar's name. The name may only contain standard letters and numbers.

2 Adding a calendar

  1. Add the Google calendar for the smart home device.