Plugin configuration has to be corrected:
E.g similar to:
<plugin>
   <extension
         point="org.knime.workbench.repository.nodes">
      <node
            category-path="depress"
            expert-flag="false"
            factory-class="org.impressivecode.depress.its.bugzilla.BugzillaAdapterNodeFactory"
            id="org.impressivecode.depress.its.bugzilla">
      </node>
   </extension>

</plugin>