My flarum also cannot transform links to video players. I tried to disable it, refresh the discussion and enable it and discussion again, then re-edit the link post and save again. Nothing works, also no error messages in browser's console.
I'm a developer, too, just not very familiar with these web things. I checked the source code, it seems like any link started with http/https and end with .mp4 should be transformed.
I understand if there's no answer of how to fix it. Just want to ask if you want me to provide any information to help debug.
