Digital Editions - Unable to Download

I'm using a MacBook running 10.12.4 and when I try and open a file downloaded from my local library I get the following error message:

Unable to Download

Error getting License. License Server Communication Problem:

E_ACT_NOT_READY

I've contacted technical support at the library who tell me its a security issue but give me no further clues or how to fix it.  Ive tried ADE versions 3 and 4.54, both fail.

Any one have an answer?

Thanks