Some common reasons that setup/connection issues occur are:
The Jira service is down.
The driver jar file, jira.jar, is not defined on your CLASSPATH. If the driver is not defined on your CLASSPATH, you will receive a class not found exception when trying to load the driver. See "Setting the classpath" for details.
The JDBC driver’s connection properties are not set correctly in the connection URL or data source. See "Configuring a data source" for more information. For example, the host name or port number are not correctly configured.