When I upload/edit any model and it includes embedded videos, they will not show up on the actual published model page. As I was going back and fixing it for all of my models, I noticed that all of them before a certain date still had the embedded videos. However, when I edited one of them, it required I uploade a cover for the app, and after that the embedded videos would not show up at all.
For a workaround, I copied and pasted the links with other non-hyperlink tests, and they didn’t autoembed, and the hyperlinks were still visible on the actual page itself. So if you’re having this problem, hope it helps! 
I’ve submitted a bug report about this.
So apparently it’s because they’re trying to combat spam via blocking short links(?), so if you use the “share” feature on YouTube to get the link it’ll block it, but if you copy and past the url from the top it’ll be fine. Their response:
"Thank you for contacting MakerWorld Team.
After conducting an investigation, we have identified that the issue is likely caused by the filtering of short links. To address this, we kindly request that you try using the following links instead.
We apologize for any inconvenience caused, and please be assured that we are actively working on optimizing this functionality.
We sincerely appreciate your understanding and patience in this matter."
