Error

Hello,

Simple Calendar is not work.

The error code
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While trying to retrieve events, Google returned an error:
Error calling GET https://www.googleapis.com/calendar/v3/calendars/9ohln3lo8rvqm46l57gi08r1fg%40group.calendar.google.com/events?singleEvents=true&maxResults=2500&timeZone=Asia%2FTokyo&timeMin=2016-09-28T01%3A00%3A00%2B09%3A00&timeMax=2017-10-26T23%3A59%3A59%2B09%3A00&key=AIzaSyC8Uc-QHeUdivags9MGmJkY_Uq6RDHCmQM: (403) The request did not specify any referer. Please ensure that the client is sending referer or use the API Console to remove the referer restrictions.

Please ensure that both your Google Calendar ID and API Key are valid and that the Google Calendar you want to display is public.
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API key, calendar ID and public check are all right.
Please tell me the cause of why this kind of thing happened.