Even the provided example doesn't work when I populate it through a SEED job via JCasC. I have a job declaration like:

job('test') {
    properties {
        ownership {
            primaryOwnerId('__my_id__')
        }
    }
}

but I see common message "Ownership is not configured for this Job. It can be configured using the "Manage Ownership" link on the left menu if you have appropriate permissions.", looking into config.xml:

<properties>
  <com.synopsys.arc.jenkins.plugins.ownership.jobs.JobOwnerJobProperty plugin="ownership@0.12.1"/>
</properties>

I'm able to manage ownership manually by myself, when I do this from UI (my_id is recognized by Jenkins itself, it comes from LDAP configuration if it's important, I'm logged-in) I see in config.xml:

<properties>
  <com.synopsys.arc.jenkins.plugins.ownership.jobs.JobOwnerJobProperty plugin="ownership@0.12.1">
    <ownership>
      <ownershipEnabled>true</ownershipEnabled>
      <primaryOwnerId>__my_id__</primaryOwnerId>
      <coownersIds class="sorted-set"/>
    </ownership>
  </com.synopsys.arc.jenkins.plugins.ownership.jobs.JobOwnerJobProperty>
</properties>

I've tried to enable an ownership mechanism like:

job(ITEM_PATH) {
    properties {
        ownership {
            ownershipEnabled(true)
            primaryOwnerId('__my_id__')
        }
    }
}

but it doesn't work as well due to ERROR: (script, line 13) No signature of method: javaposse.jobdsl.dsl.helpers.properties.OwnershipContext.ownershipEnabled() is applicable for argument types: (java.lang.Boolean) values: [true].

Just a wild guess - adding a missed method in helper groovy class can fix all of this?

  
Note: _my_id_ should be replaced by real one.