The webapp didn't start correctly for the following reason :
Error initializing Spring Context Service
fr/paris/lutece/util/signrequest/NoSecurityAuthenticator has been compiled by a more recent version of the Java Runtime (class file version 55.0), this version of the Java Runtime only recognizes class file versions up to 52.0 (unable to load class fr.paris.lutece.util.signrequest.NoSecurityAuthenticator)