Error

Hey, I have this plugin set up for years and no I am trying to switch to grouped calendar. When I am trying to add new calendar, I get this error.

While trying to retrieve events, Google returned an error:
{ “error”: { “errors”: [ { “domain”: “global”, “reason”: “notFound”, “message”: “Not Found” } ], “code”: 404, “message”: “Not Found” } }
Please ensure that both your Google Calendar ID and API Key are valid and that the Google Calendar you want to display is public.

Since one calendar is already working API key must be ok, and I also used ID of public calendar. So what is next?