Do you have any other module installed for your MusCol? (e.g. Random album, Recently added Album etc) Try disable all of them and see if your player shows up.

And for which view are you having this problem? Individual song or album?

individual songs, jwplayer plugin doesn't like files with weird characters. The file name is the same as in the name in the picture "Panama'm Tombe"

For individual song the fix is different. You need to use another fix due to how jwplayer treats encoding

Download this file and unzip it under plugins/muscolplayer/. This will create a file called jwplayer_helper.php file.

Then go to jwplayer.php in the same directory and change line 127 to

s".$unique_id.".addParam('flashvars','file=" .utf8_jwstr($song->filename)."&duration=".$song->length . $string_params . "&autostart=false');

Basically utf8_jwstr function is an encoding function I wrote that handles jwplayer encoding. See if that works.

I did exactly as you suggested but no I get a blank page when click on the song name.
I replaced line 127 with this : s".$unique_id.".addParam('flashvars','file=" .utf8_jwstr($song->filename)."&duration=".$song->length . $string_params . "&autostart=false');
And Jwplayer_help.php was copied into the plugin folder.