Logback json configuration return no logs

Question

I'm trying to get json logs from Nexus 3. Since it use logback, I tried ton change the logback.xml file but, for some reason, it result to no logs at all... Does someone know what I did wrong?

The only things I changed is to add those lines to the Nexus's default logback.xml file, to add json logs:

      <appender name="json" class="ch.qos.logback.core.ConsoleAppender">
        <filter class="org.sonatype.nexus.pax.logging.NexusLogFilter" />
        <layout class="ch.qos.logback.contrib.json.classic.JsonLayout">
            <jsonFormatter class="ch.qos.logback.contrib.jackson.JacksonJsonFormatter">
                <prettyPrint>true</prettyPrint>
            </jsonFormatter>
            <timestampFormat>yyyy-MM-dd' 'HH:mm:ss.SSS</timestampFormat>
        </layout>
      </appender>

and change these for logback to actually use it:

<root level="${root.level:-INFO}">
    <appender-ref ref="osgi"/>
    <appender-ref ref="console"/>
    <appender-ref ref="json"/>
    <appender-ref ref="logfile"/>
    <appender-ref ref="clusterlogfile"/>
    <appender-ref ref="tasklogfile"/>
    <appender-ref ref="metrics"/>
  </root>