cannot download music album via google play on medion junior tab S7316

help please, i am trying to download Christmas album for my 9 year old who wants to learn "Walking in the air". when click to buy it comes up with Error ... error while retrieving information from server (RPC:S-7:AEC-0)

any ideas? tried downloading from PC and no problems and i'm no techie and don't know if i buy and download to PC can i then transfer it to the Medion tab?

thanks Tina