Concurrent use license manager cannot be reached

I have ten concurent use ArcInfo Desktop licenses installed on a server machine. It works well on the server. The 10 licenses are available when we check from ArcGIS administrator. But now I need to use of the license on another machine on the same network. The license administrator cannot connect to the license manager machine saying "invalid Host ID". Hence I cannot use one of the 10 concurrent use license. Any idea of what I need to do?
Thanks
Tunrayo