Here are some scenarios where operations may be disallowed:
Classic registries are no longer supported. Please upgrade to a supported service tier using az acr update or the Azure portal.
The image or repository maybe locked so that it can't be deleted or updated. You can use the az acr repository show command to view current attributes.
Some operations are disallowed if the image is in quarantine. Learn more about quarantine.
Your registry may have reached its storage limit.