4 haters only
https://www.youtube.com/watch?v=TfM6c1NJLs8
https://www.youtube.com/
^ this is the website
watch?v= TfM6c1NJLs8
^ this is basically a subpage telling the website that you're wanting to watch/watching a video, v= (video equals) and then the video label/ID
So, what the BB code, [YOUTUBE] does is basically tell the forum to show/go to https://www.youtube.com/watch?v=
So all you need to enter is the video label/ID into the forum BB code which are the letters/numbers that come after v=, in this case it's TfM6c1NJLs8
The way you're trying to enter it in is basically having the forum go to,
https://www.youtube.com/watch?v=http...?v=TfM6c1NJLs8 (because it's doing the www.youtube.com/watch?v= + whatever you're entering between the BB code.)
And ofc, it's not showing any video on the forum because when you try going to that URL it says the video doesn't exist because the link isn't a valid link.
I hope that explains why you can't seem to get the video working in your posts.
4 haters only