Sorry for cursing, but it's clearly a dev bug.
You actually have to edit manually gapi.php file on lines 135 an 164 , remove "true" , go back to the backoffice to config the Google API module - btw it gives an immediate error notice - insert the user Analytics data, then google asks you to select the Google account (yes, there are people that have more than one Google account) and only then the Google analytics API asks you to opt-in to associate the Prestashop store.
Then - to clean the BUG notice - you have to go back to gapi.php and re-write "true" on on lines 135 an 164 again.
Does this procedure make sense???? No.