As long as you are using Now X 10.0.4 there won't be any registration server issues. To download that version, go to www.nowsoftware.com.
If you are using 10.0.4, the problem will likely be written out to the console. In that case, start Now X and if it fails to launch, go to /Applications/Utilities/Console.app, open it, and save a copy of the console log (File menu), then email that console log to email@example.com along with a description of what is happening.
NOTE: Now X is launching fine for me on all of my test computers on a home network.