Autocad network license manager error

I was having a tough time with the following error in many systems on a trusted domain within our network. The Autocad licensing server was on our domain and could be accessed without issues from the client desktop which was on the trusted domain, but AutoCAD wouldn't start. It just kept popping up this error

The network license manager was not able to get a valid license. If this problem continues, please contact your system administrator. Error [1.5.-18]

Turned out that, in the AutoCAD server license file, the server name provided was not accessible from the client desktop since it was not in a FQDN format. When the hosts file was modified to do the name mapping, it worked fine. I then created a host record in the trusted domain with the same name to point to the licensing server and it worked.