This really helped me. The major breakthrough is ` Additionally, make sure you have the blobKey path (from your response mapping) specified under advanced settings.`
Learning here is: Celigo stores the `blob` content temporarily in a file system somewhere, with a reference to it. This reference is what the mapping refers to. And, finally the key-name referenced in the advanced settings, actually refers and fetches the blob/biniary/non-json data of interest.
Thank you.