Answer 1

Maybe SL had disabled it.

[1]. Warning: Because each browsing context is a complete document environment, every <iframe> in a page requires increased memory and other computing resources. While theoretically you can use as many <iframe>s as you like, check for performance problems.

[1].
https://developer.mozilla.org/en-US/docs/Web/HTML/Element/iframe

[2].
https://blog.logrocket.com/the-ultimate-guide-to-iframes/

Answer 2

Romeo Cojocaru
From console it seems site blocked it!

https://code.sololearn.com/W0o5cYE3A767/?ref=app