If you receive error messages from Google when trying to open the Google Webmasters Tools/Search Console integration, ensure that the account used to login to Google is the same account associated with the website domain in Google Webmasters Tools/Search Console and that the domain specified is exactly the same registered in Google Webmasters Tools/Search Console. The domain must match exactly, so if you have registered http://www.mydomain.com and your are requesting for example http://mydomain.com Google won't allow the access.
In this case you could receive an error message: '(403) User does not have sufficient permission for site 'http://www.sitexyz.com/'
You can set preferred domains for Google Webmasters Tools/Search Console (and Google Analytics) in the component configuration section as visible below:
Also if you are updating from a previous version of JSitemap and you already have an ongoing login to Google used to access the Google Analytics stats, you must logout and perform a new login. This is required because now the application needs permissions for both Google Webmasters Tools/Search Console and Google Analytics.
Finally, if you have setup your own Google Application ensure that both API for Google Webmaster Tools/Search Console and Analytics are enabled in the Google console.
As a side note, after an update from a previous version of JSitemap, it would be ideal clearing the browser cache to have all the panels used in the Google Webmasters Tools/Search Console dashboard expanded automatically by default.