When accessing Google Analytics in JSitemap. Should you get the following error message:

Error calling GET https://www.googleapis.com/webmasters/v3/sites/http%3A%2F%2Fwww.mypage.com/sitemaps?key=mykey: (403) User does not have sufficient permission for site 'http://mypage.com/'. See also: https://support.google.com/webmasters/answer/2451999.

SOLUTION

Go to JSitemap Configuration > Google Webmasters & Analytics. Enter the domain name of the site x 3!!!

ALSO and very important make sure that the domain has been added at :

https://www.google.com/webmasters/tools