Appointments Plus: GCal Integration

Hi, I'm using A+ on a client site and trying to get it to sync with GCal. I've gone through the steps to install the OAuth key, etc. but am still getting errors when I click "update calendar". For example:

Fatal error: Uncaught exception 'Google_ServiceException' with message 'Error calling GET https://www.googleapis.com/calendar/v3/calendars/%20flcl0rmkd1an0seg7fcfvu0iao@group.calendar.google.com/events?timeMin=2013-02-12T20%3A34%3A27%2B00%3A00&singleEvents=true&maxResults=100: (404) Not Found' in....

Thanks!
Steve