So I've been having a pretty long-lasting issue with one of my forums for a good while (maybe since 4.2? not sure, been too long to remember).
If I paste a link to anything, the link will not embed, at all. Not even as just a simple clickable URL, nothing. I have to click the link button and add it manually - and certain things like Gyazo or other Image link embeds are essentially impossible.
Link embeds are enabled for the group and for the site itself, and the issue happens regardless of CKEditor theme.
It's really annoying and I'm hoping someone here has an idea of where to look to find the issue.