title: Why do I get ImagePullBackOff unless I specify specific tag version?
body: <p>If I attempt to create a Pod using the latest version of an image from Azure Container Registry, i get a "ImagePullBackOff" error. If I explicitly specify the image version, the Pod is created successfully. </p>
  
  <p>I have created a new Image Pull Secret and can confirm that Kubernetes is pulling the image from ACR as the Pod starts up successfully when setting the version. When I set the image name to ACR_ImageName:latest (or when ommitting :latest, or when setting the imagePullPolicy to "Always", the pod fails to create reporting the following error: <em>note that i have replace the acr name and image name</em></p>
  
  <blockquote>
    <p>Warning  Failed     27m (x3 over 28m)      kubelet, aks-agentpool-15809833-vmss000007<br>
     Failed to pull image "acrPath/imageName": [rpc error: code = Unknown desc = Error response from daemon: 
     manifest for acrPath/imageName:latest not found: manifest unknown: manifest unknown, rpc error: code = Unknown desc = Error response from daemon: 
     manifest for acrPath/imageName:latest not found: manifest unknown: manifest unknown, rpc error: code = Unknown desc = Error response from daemon: 
     Get <a href="https://acrPath/imageName/manifests/latest" rel="nofollow noreferrer">https://acrPath/imageName/manifests/latest</a>: unauthorized: authentication required]</p>
  </blockquote>
  
  <h1>This DOES NOT works</h1>
  
  <pre><code>apiVersion: v1
  kind: Pod
  metadata:
    name: k8spocfrontend
    labels:
      app: k8spocfrontend
      type: frontend
  spec:
    containers:
    - name: k8spocfrontend
      image: dteuwhorizonacrhorizonmain.azurecr.io/k8spocfront:latest
      imagePullPolicy: "Always"
    imagePullSecrets:
    - name: acr-auth-poc
  </code></pre>
  
  <h1>This works</h1>
  
  <pre><code>apiVersion: v1
  kind: Pod
  metadata:
    name: k8spocfrontend
    labels:
      app: k8spocfrontend
      type: frontend
  spec:
    containers:
    - name: k8spocfrontend
      image: dteuwhorizonacrhorizonmain.azurecr.io/k8spocfront:2617
      imagePullPolicy: "Always"
    imagePullSecrets:
    - name: acr-auth-poc
  </code></pre>
  
  <p>As you can see from the pods below, the pods gets created when setting the version tag.</p>
  
  <blockquote>
    <p>k8spocfront-5dbf7544f8-ccnxj | 2/2 | Running | 0 | 33m</p>
  </blockquote>