Ok, I just saw that all Videos seems to work when I type the full code.
For example this is shown as embed:
www.youtube.com/watch?v=zcy1DR6gr-U
Right below I posted this code (the code of all of my old videos)
{youtube}zcy1DR6gr-U|500|300{/youtube}
but it shows only the code.
What should I do? The plugin needs to be customized? If yes then how? My old developer had customized it but I don't know how to do it.
Thanks.