It seems JAVA_HOME environment variable was not properly set after JDK package installation. (If you are sure, JDK is installed as it is one of the main pre-requisite to make jasper_erpnext_report module work)
You can setup JAVA_HOME all users, I would recommend placing the following line in /etc/profile
export JAVA_HOME=$(readlink -f /usr/bin/javac | sed "s:/bin/javac::")
source /etc/profile
This will update dynamically and works well with the alternatives system.
Note: The update will only take place in a new login shell, so Logout and Log Back to Shell to make this new environment variable work.
And then try to run plugin setup steps one more time and also follow instructions to troubleshoot: Jasper Report: KeyError: 'JAVA_HOME' - #2 by luisfmfernandes