There’s a specific script for Replit oneboxes:
When we paste a Replit link, the composer shows the expected result:
When the post is processed, the link is transformed into an empty iframe.
<iframe width="695" height="521" frameborder="0" data-unsanitized-src="https://replit.com/@Firepup650/Yeehaw?embed=true" seamless="seamless" sandbox="allow-same-origin allow-scripts allow-forms allow-popups allow-popups-to-escape-sandbox allow-presentation">
#document
<html>
<head></head>
<body></body>
</html>
</iframe>
I don’t know if the issue comes from Replit or from the onebox script. I’d guess it’s the script, but I’m no coder 
The link has proper opengraph tags, though: https://developers.facebook.com/tools/debug/?q=https%3A%2F%2Freplit.com%2F%40Firepup650%2FYeehaw