In rare instances, the Java install on the server machine may not install properly, or more likely, the installed version of Java is not compatible if you are running an older version of LabTutor Server. ADInstruments has been including the most current version of Java with the LabTutor Suite installer files since LabTutor version 4.1, so updating to the latest version of LabTutor Server should resolve the issue. If you need to keep using the old version of LabTutor Server for some reason, you will need to uninstall the current version and reinstall the appropriate version of Java on the machine to resolve the issue.
If the steps above do not solve the issue, please contact ADInstruments Technical Support.