@Jean Charles, Didier (-AZ-) Apologies for the delay in response and all the inconvenience caused because of the issue.
You need to have certain roles configured to pull the image. As mentioned here below are the roles with their respective capabilities:
You can assign the role accordingly. Also I would recommend you to go through this as well which talks about Azure Container Registry webhook. As mentioned The endpoint for a webhook must be publicly accessible from the registry. You can configure registry webhook requests to authenticate to a secured endpoint. You can configure it accordingly as mentioned if not already done.
Hope it helps!!!
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