When I launch a client in the Native Client Launcher and logon I only get a grey screen. I see in another topic that it can help to delete the .ignition folder in c:\users\username but that didn’t help.
We need a bit more information to help with this. Is this a new project, or has it worked previously? What version of Ignition are you using? What Java version if Ignition is less than 8.0? What Operating System?