JAR runs from Terminal but not otherwise

I have an old JAR file , signed but its signature has expired and authors no longer give updates and will not help with the JAR

It runs in Terminal using the command ‘JAVA -JAR filename’ but I cant run it in any other way.

It uses Oracle Java 8 (installed on my Fedora 37) and also set as current java.

This JAR is associated with an JNLP file - the JNLP does not run at all and the error message is that ‘unsigned applet’ not allowed.

What is the solution?

Thank you