Google Calendar Integration Issues

Hello,

Can anyone help! I have been trying to integrate Google Calendar with Appointment Lite and I cant get it to work.

I keep getting this error in the Log:

[13/08/2016 6:50 pm] Error refreshing the OAuth2 token, message: ‘{
“error” : “invalid_grant”,
“error_description” : “Invalid JWT Signature.”
}’
[13/08/2016 6:50 pm] Error calling GET https://www.googleapis.com/calendar/v3/calendars/admin@call4backup.org/events?timeMin=2016-08-13T18%3A50%3A37%2B00%3A00&timeMax=2017-08-13T18%3A50%3A37%2B00%3A00&singleEvents=true&maxResults=500&orderBy=startTime: (401) Invalid Credentials

I have tried to play around with it but as Google API’s has been updated since the flow chart was written its hard to know if I have followed the steps correctly, or what these errors are telling me is wrong.

Can anyone give me a simple step by step way of fixing this issue??

Thanks in advance
Rob