Can't get Google Calendar to Work with Simple Calendar

I would like to use Simple Calendar instead of embedding my Google Calendar directly to my website- https://www.hillsidechurch.ca/calendar. I do find it strange that my calendar ID in Google Claendar settings is the same as my email address, but it is for sure set to “public”. I followed the directions to create an API key. This is the error code I’m getting:
While trying to retrieve events, Google returned an error:
Error calling GET https://www.googleapis.com/calendar/v3/calendars/hillsidechurch1166%40gmail.com/events?maxResults=2500&timeZone=&key=AIzaSyDP1zt8fUVNZCjOM7fM1fxg3WwYaLS-UWA: (403) There is a per-IP or per-Referer restriction configured on your API key and the request does not match these restrictions. Please use the Google Developers Console to update your API key configuration if request from this IP or referer should be allowed.

Please ensure that both your Google Calendar ID and API Key are valid and that the Google Calendar you want to display is public.

Any help is much appreciated!