eReader help

Hi can any one help with my problem?  I have been trying unsuccessfully to read a purchased book from Waterstones on my eReader. (pandigital multimedia tablet & eReader) It came with an app for B&N bookstore but this I can not use being in the Uk.  So downloaded ADE on my pc and activated it and my eReader it downloads to my pc fine but goes to the B&N libary and when I try to open it I get  device not activated (EADEPT_CORE_USER_NOT_ACTIVATED urn:uuid:56083_20da-41e7-9488-2dcc64c5df97;0.