Can't open .acsm file with ADE on Mac "Connection Error Detected"

I am a distributor supplying all of France public libraries.

My customers on Mac complain that they can't open our .acsm files. I have the same experience.

I have Mac OS Catalina 10.15.4 and previously Mojave 10.14.6 and it didn't work on any of them.

When I try to open any .ascm file, I get the same error message : "Connection Error Detected
Digital Editions could not connect to the fulfillment server. Please make sure you are connected to the internet."

- My internet connection is just fine.

- Our ebook server works well.

- Date and time are correct

- The ADE server is up and running

- The .ascm files are fine, no problem with them.

I tried

- restarting the computer,

- uninstalling and reinstalling ADE,

- unauthorizing and reauthorizing my computer,

- installing older versions of ADE doesn't work - I get a message that the app needs updating

but it didn't work.

I see on this forum that the problem has been going on since 2013, that there are 7 pages of similar complaints and ZERO resolution. I receive hundreds of complaints from our customers. This is a disgrace. I will need to switch DRM if Adobe doesn't provide any solution.