Litalino on your page I see one video player, and one [embed-video] tag that is not converted. Are both supposed to be embedded with this extension or is a different extension responsible for the first video player?
The block of text containing the [embed-video] tag seems to be inside of a code block. That would explain why Flarum keeps the original text and does not transform it. Make sure you don't have 4 spaces in front of the text or a bbcode/markdown code block delimiter above the tag.
If in doubt, can you share a screenshot or exact copy of the text inside of the post write/edit text input?
Your php flarum info would also be useful to see other extensions used at the same time.
