That’s because you didn’t link the topic, the /3 at the end means you were linking directly to a reply. You can see exactly what Facebook is going to pick up using their developer sharing debugger.
Topic link: https://www.helloforos.com/t/algunas-fotos-de-mi-experiencia-en-el-dorado-world-tour/472432/
Reply link: https://www.helloforos.com/t/algunas-fotos-de-mi-experiencia-en-el-dorado-world-tour/472432/3
This is the embed if you share the correct link to the topic:
Topic OG data:
Reply OG data:
Checking the FB cache, the direct topic URL in question has never been shared to them, the link you gave above is the exact url they’ve cached previously.
It looks as though the OG tags only include images for the first post in a topic, otherwise it reverts to the avatar, even if that reply includes an image. I can’t comment as to whether that’s the intended behavior, but as Jeff says the topic links do include the first image within their data.
That said, it wouldn’t make sense for replies to embed the image - there’s no context and it would confuse the user when they click through to the page and can’t see it without scrolling all the way up.