Adobe ID not working on some books

I am at a loss. I have followed all the guides on the Kobo website and I still have had no luck.

I am using Adobe Digital Editions to load books purchased off the Kobo website onto my Kobo Glo. My computer is authorised and my Kobo is authorised.

The books can be opened on my PC on both the Kobo and PC library menus. However whenever I unplug my Kobo and try to open a book it says it doesn't have permission!

I am at the end of my tether and considering wiping everything and starting again. Does anyone have any other tips for getting it to work?

DRM is a pain in the ass!