We are attempting to send ecards for every successful donation API call. At the moment, donations go successfully and other autoresponders work but ecards. Why are ecards not sent with a successful Donation API call?
Make sure your donation API call has all parameters that are required for the the ecard to be sent and that correct values are sent with these parameters. In particular for "ecard_id" make sure you are passing stationary layout ID and not email campaign ID. Note that information on specific parameters to be passed is available on API documentation for donations.