Updating Norton Premium subscription on Android tablet

Hello  I have purchased a new subscription for Norton Premium and have had no trouble updating it from within my account for laptops and a mac.  This was simply a case of clicking on the device and then choosing the option to enter a new product key.

However this option is not available for my tablet, I cannot find any means of updating the subscription either through the website or within the Norton options on the tablet.  It now has 6 days left of the old subscription - any ideas.  I have even tried going through the google store but although I have downloaded it again from there at no time was there any request for my key and every time I try to get into it through the store it tells me to uninstall first even though I did choose that option.  My actual installation does not seem to have changed. - any ideas- there must be something simple I am missing.  I don't remember having a problem setting it up initially on the tablet a year ago.