Grafana alert with image on mail

i have a mysql db which feeds grafana (v9.2.4). i am trying to send grafana alerts with dashboard panel screenshots. somehow i am only getting blank pages on email.

i am new to grafana alerting. this is how my rule looks like

also, on the dashboard page, i see this - so definitely

i am setting alert on the right panel. can some1 suggest if i am missing a setting or something.