The notification does not have image_url for webhook

I upgrade the new grafana for 9.0.6, and installed the image renderer 3.5.0. When i recive the notification for webhook, the content does not include the image_url. the image render is worked. because i found the image data in my s3 bucket. i’m already configurator the [unified_alerting.screenshots]
capture = true
upload_external_image_storage = true

my datasource is prometheus.
does something i missed? pls help me, thank you very much