Please help me. The Acsm file is not downloaded.

I am a student studying, I received an Acsm file as a textbook.
Before, I studied by opening the acsm file with Adobe digital edition, but I received a new file with different contents, so I opened it again this time, and it is not downloaded.

Here's how to guide:

Error getting License. License Server Communication Problem:

E_LIC_LICENSE_SIGN_ERROR

I want to study quickly, but I can't proceed. Please help me.

Thanks.