You have a computer that does not have access to the internet or is in a closed network where there isn’t any internet access or even when the machines are unable to whitelist all the Autodesk sites required to use a single-user license.
You have already gone through these Autodesk articles:
Due to security limitations you are unable to work with the single-user license or get it to run.
The Single-User licenses require communication with the Autodesk servers from time to time.
What you can do is buy a Multi-User (MU) / Network license instead of a Single-User license instead. The MU license does not require an internet connection, just a MU license generated online from another machine or emailed to you from Autodesk.
If you are in an enclosed network then you can install the license manager on a server and on a machine that does have internet access generate a network license file and save it to an external device to take into the “closed network” and get it up and running.
If it’s just one machine, then you can install the license manager on that one machine and obtain a network license from Autodesk and port it to that one machine to get it up and running.
This Autodesk article and have either your Contract Manager (CM) or Software Coordinator (SC) generate it for you.
There are several methods mentioned in the above article.
To install and get the license manager up and running please see these articles: