Just like troubleshooting anything else ...first disable ALL add-ons and test again. If it works, then turn them back on one-by-one to find the culprit - report issue to add-on developer.
Edit: By the way what version of XenForo are you running?
Just like troubleshooting anything else ...first disable ALL add-ons and test again. If it works, then turn them back on one-by-one to find the culprit - report issue to add-on developer.
Edit: By the way what version of XenForo are you running?
I copied and pasted a link right into the editor. It just posts the link and no longer embeds the video player. When I try to inset it via the media link, it says YouTube isn't allowed.
For anyone else who struggled with this problem and found their way to this thread the issue is orphan s9e addon rows were in the xf_bb_code_media_site table from before the upgrade - should have uninstalled it (rather than disabled it) before upgrade.