Using Adobe Digital Editions to download library books and then to my Kobo

I use ADE to download books from my local library and the transfer them to my Kobo Glo to read them. Recently the Kobo says I am not authorised  to read them.although I can still read them in ADE. I used AdE to de-authorise the Kobo and then re- authorise it but it still doesn't work. I have tried deleting the books from both devices and reloading them but to no avail. I see someone had a similar problem last year but there was no solution recorded. Does anyone have an answer?