Getting error 'failed to execute when condition: cannot fetch phase from <nil>' with Argo CD notifications - kubernetes

Question

I have installed a brand-new Argo CD (v2.1.7) and notifications (v1.2.0). I configured it to send me a Slack message and subscribed my application to the on-deployed trigger using the following annotation:
annotations:
notifications.argoproj.io/subscribe.on-deployed.slack: my_channel
When I deploy my application, the log output of the argocd-notifications-controller is:
time="2021-12-10T12:18:23Z" level=error msg="failed to execute oncePer condition: cannot fetch syncResult from <nil> (1:27)\n | app.status.operationState.syncResult.revision\n | ..........................^"
time="2021-12-10T12:18:23Z" level=info msg="Trigger on-deployed result: [{[0].y7b5sbwa2Q329JYH755peeq-fBs [app-deployed] false}]" resource=argocd/ah-ctp-argocd-test
time="2021-12-10T12:18:23Z" level=info msg="Processing completed" resource=argocd/ah-ctp-argocd-test
time="2021-12-10T12:19:21Z" level=info msg="Start processing" resource=argocd/ah-ctp-argocd-test
time="2021-12-10T12:19:21Z" level=error msg="failed to execute when condition: cannot fetch phase from <nil> (1:27)\n | app.status.operationState.phase in ['Succeeded'] and app.status.health.status == 'Healthy'\n | ..........................^"
As a test, I changed the when condition to when: true and added {{ .app }} to the message body, then re-deployed. I received the notification in Slack, however {{ .app }} does not contain operationState. It does contain, for instance app.status.health.status and its value is 'Healthy'.
I see no one has posted any similar error online, which leads me to think I must be doing something wrong. Does anyone have any advice?

Answer 1

Okay, so this was a PEDKAC error. I received a notification the first time, but never again. It turns out that Argo CD keeps track for which commits it has sent notifications. The problem was that I was deleting and redeploying the app in Argo CD, but it was always the same commit. When I created a new commit and deployed from that, the notifications came through as expected.

Answer 2

For me the same errors appeared when I had wrong values in the arocd-notifications-cm config map.
I was using unquoted value for apiURL which I was not using anyways. Once I removed (commented) the apiURL entry in service.slack, everything started working well.