Impossible to set a post thumb to a card post

[bloute]

I'm using Make (ex-Integromat) to multiple post news on my social media.
For Bluesky, I'm using this process https://community.make.com/t/rss-feed-to-bluesky-cards-post/61794

I keep receiving this error:
Error: 400 Bad Request
{“error”:“InvalidRequest”,“message”:“Invalid app.bsky.feed.post record: Record/embed/external/thumb should be a blob ref”}

Although Record/embed/external/thumb seems indeed to be a blob ref.

Here is below the json that I send:
{"repo":"did:plc:e7fi7z322ol6oxxbow36ca4s","record":{"text":"My text https://www.google.fr","$type":"app.bsky.feed.post","embed":{"$type":"app.bsky.embed.external","external":{"uri":"https://www.google.fr","thumb":{"ref":{"$link":"bafkreif7ps2sk6tbfe2s24g5tu4arehaqzwaklb63kh7yncxqi3w7pccqy"},"size":"94055","$type":"blob","mimeType":"image/jpeg"},"title":"My Text","description":"My description"}},"createdAt":"2025-01-17T08:49:46.003Z"},"collection":"app.bsky.feed.post"}

Is it possible that my repo is broken like #1089 ?