I notice that the portal is not currently doing a package step when building via maven, which means that the main jar in not being included in the build snapshot. I have limited knowledge of maven, but as far as I know, if you can please change the build command from:
C:\Maven\apache-maven-3.3.9\bin\mvn.cmd clean compile assembly:single -e
to
C:\Maven\apache-maven-3.3.9\bin\mvn.cmd clean compile package assembly:single -e
it should all work. I suspect you can even just replace compile with package.