Error retrieving license. Communication problem with license server: E ADEPT UNKNOWN

For several days now I have received the following message when I want to download an e-book: Error retrieving license. Communication problem with license server: E ADEPT UNKNOWN.

I have already performed the following actions without success:

1. remove authorization and reauthorize computer;
2. Uninstall ADE software and reinstall it.

I also waited a few days, assuming that the license server was actually unreachable, but that doesn't seem to be the case.

A similar problem was reported in this community in 2016. The solution offered was to edit the registry (remove ADEP key), but the entry in the registry has been changed as far as I could see.

How can this problem be solved?

The website I downloaded the e-book from only supports ADE.

Thanks in advance and kind regards,

Stef