Sony E-Reader DRM Issues
I have had the same issue with my e-reader and the library program. You have to make sure your Adobe ID is current. The Adobe ID is the DRM for Sony e-books. An Adobe ID should already be associated with your account. Tech support or help menu says you have to de-authorize and then re-authorize your computer and device. Unfortunately, that solution has not always worked for me, so I had to call tech support and have them do it on their end.
The issue seemed to be more of a problem after updates to the software and reader. I have had this happen multiple times.
I have enjoyed the reader, hate the library management and DRM issues.
It's a pain in the tookus.
Hope this helps if you haven't already resolved the issue.