ArgoCD not triggering notification on sync success

Question

I am trying to set up a notification for older argocd version 2.4.15, but keep struggling with this behavior:

level=info msg="Processing skipped: sync status out of date"

It happens whenever a new commit is synced and the app is deployed.

I have an argocd-notification ConfigMap:

data:
  context: |
    argocdUrl: #REDACTED
  service.webhook.mattermost: |
    url: #REDACTED
  subscriptions: |
    - recipients:
      - mattermost
      triggers:
      - on-deployed

and here is a trigger:

  trigger.on-deployed: |
    - description: Application is synced and healthy. Triggered once per commit.
      oncePer: app.status.sync.revision
      send:
      - mattermost-app-deployed
      when: app.status.operationState.phase in ['Succeeded'] and app.status.health.status == 'Healthy'