Adobe DRM-protected content

I have an Adlibris Letto reading pad from Sweden. I bought a book from google play store and after purchase dragged it into the library of the Letto via Adobe Digital Edition. Its in the library like every other book, but when I try to open the book, it says a message "Unit authorization is needed to access Adobe DRM-protected content". The account is authorized on me jakobtegstrom1@gmail.com, but it still says this message. My sister bought this pad for me for present, maybe her account is linked to this? Maybe that the pad is aouthorized to my sisters account, but the purchase on google stands on me instead and when I try my sisters account it doesnt match with the vendor ID from google play. Please contact me ASAP.