When trying to download books on e-book-reader by using Adobe ID it says "Authorisierung überschritten" - more than six hardwares connected - although there are only two hardwares connected. No list of hardwares to be found anywhere to check what is

When trying to download books on e-book-reader  by using Adobe ID it says "Authorisierung überschritten" - more than six hardwares connected - although there are only two hardwares connected. No list of hardwares to be found anywhere to check what is meant and no idea how to correct this mistake!