Not sure this applies to your configuration, but for our server, we would use "https://ourdevserver.edu/labkey" ("/labkey" added). When I remove "/labkey" on our server I get:

Exception in thread "main" org.labkey.remoteapi.CommandException: Not Found
    at org.labkey.remoteapi.Command.throwError(Command.java:355)
    at org.labkey.remoteapi.Command._execute(Command.java:321)
    at org.labkey.remoteapi.Command.execute(Command.java:202)

which sounds like your error.