Unable to download

Would be very grateful for any advice. I have been unable to download a book from my local library to my Kobo on my MacBook Pro. I have not had this problem before. The authorisations for my MacBook and my Kobo say they are both authorised.

This is the message I am getting 

Unable to download

Error getting License. License Server Communication Problem:

E_AUTH_BAD_DEVICE_KEY_OR_PKCS12

Many thanks for any help in advance.