Thank you for bringing that to my attention mate. It appears the error is due to the absence of the bundled Java Runtime Environment (JRE).
To resolve this, open Launch4j, go to the 'JRE' tab, check 'Bundle JRE with executable,' specify the required version, and click 'Build Wrapper' again. This should ensure the generated .exe includes the necessary Java environment. Let me know if this doesn't work...