ADE e-reader authorisation does not work

I am running ADE 4.5.1.133054 on Windows 7

I am using a KOBO e-reader.

I am regularly loading e-books from the library and usually it works okay.  Today, after loading a library book I could not open it on the e-reader as the DRM info did not match my device authorisation. (it opens fine on my PC running ADE).  I erased the authorisation on the e-reader using the Device Options menu on ADE.

When I try to re-authorise the e-reader, ADE sees it and I can go to the Device Options menu, but nothing works - cannot authorise, cannot read the device authorisation info.

I would appreciate any suggestions