Facebook show post works fine, Insta does not

On the website: Meisterbetrieb in der Denkmalpflege und Restaurator im Handwerk which will soon be: https://holzbau-atelier.com I habe placed a insta icon and a fb-icon, both of them link to their popups as a lightbox each. Facebook shows the latest post as expected and intended, insta shows only “watch this out on instagram”:

Although it is setup to show the latest post, it does not, however - since I did now set it up to “-1” and set it back to “0-letzter” (0-most recent?) it shows inside sparkles-design window the post as intended.
Is this a hiccup inside insta or sparkle or something to always play around, each time the site is updated?
Finally, uploaded, it does not show the insta post inside the site but steps outside to instagram, which would not be intended but of course, if instagram handles it like this, well …

Thanks in advance,

Let me add how it looks like in sparkle:

Bildschirmfoto 2023-05-09 um 17.11.17

Thanks in advance,

Just checking @UweRausB, you have also connect Instagram in your Settings / Instagram?

I think so, otherwise I would not have the first image of screenshots, I guess:

This screenshot shows the last post actually, but does not show, once the site is uploaded.
It might have something to do with the “troubleshooting” from here?

And also it would not show “view this post on instagram”, right?

But the Facebook popup works just fine so I am not aware of any blockers and like I said yesterday, at a certain time, the site was showing up in my browser, the last post appeared. As my client as well as me have the same issue it also might not be a bad WLAN or web connection, …?

Thanks in advance,