This is probably your metadata adapter refusing the authentication and returning an unspecified error. Remember that CreditsException accepts only negative numbers as error codes, positive numbers are truncated to 0 (they are reserver for use by Lightstreamer).

If you don't have a logging system for you metadata adapter, you may set the logger LightstreamerLogger.connections.http at DEBUG level to have some clues. But beware: it's quite verbose, avoid doing it on a production server under load.