This site stated:
License Not Found Errors
Normally, the JasperReports Server installer includes an evaluation license file that you replace with a commercial license file, as described in Installing a New License File. If JasperReports Server returns an error after you replace the license file, the most likely causes are:
• You didn't clear your application server’s work directory, as explained in “Installing a New License File”. Delete the work directory, restart the application server, and try logging into JasperReports Server again.
• The Djs.license.directory property in your application server startup environment is incorrectly set:
For example, in Windows the correct setting looks like this:
In Linux, the correct setting looks like this:
The specified directory must contain the license file, named jasperserver.license. The property is typically set for your application server in the environment startup script. It must contain the location of your license file, which is usually the <js-install> directory:
<tomcat>/bin/setclasspath.bat/.sh or bin/setenv.bat/.sh
<jboss>/bin/run.bat or .sh
We copied in the license that causes the null error, then deleted the work directory, then restarted tomcat.