This is the link:
https://www.instagram.com/p/CArDzTSnZEWJJj0oW8ayeHpYBFtWgH2u8JQ10g0/
In my forum:
AI-generated summary
The Instagram onebox feature is not working on some Discourse forums. PaulinaMX initially reported the issue with a private link, but also experienced the problem with public profiles. justin confirmed the issue on Meta. However, PaulinaMX found that the onebox works for certain links, such as _https://www.instagram.com/p/CBlxjxXJ2K_/. WaitroseCarpark also experienced the issue and found a possible cause in a Meta thread about Facebook and Instagram oneboxes failing due to a change on October 24, 2020. WaitroseCarpark updated their site according to the thread but still encountered the issue, with oneboxes displaying only the ‘@’ symbol.
I don’t know much about Instagram but that looks like you’re linking to private content with login required.
Can you try other links?
Thanks, but I tried with any public profiles and is the same.
Here it’s working. 
https://www.instagram.com/p/CGsvWioH3GN/
Is it just me or is Insta oneboxing not working? On my own site and here on meta)
Probably due to this here:
Updated my site according to this thread
Still get a problem, oneboxes now show like this with just the ‘@’ (link to my site):
Bizarre, they show up ok here:
https://www.instagram.com/p/CH5zC6UFxLe/?igshid=h246yskb4u5j