[Plugin: JW Player for WordPress] It doesn' t load any video

Hello there, I have tried everything that I could but there is no way to make it working. The player is displayed, the thumb preview image is displayed, but the video is going to load forever.

you can see my test here:

https://nemoprincess.it/pianosolo/2012/01/28/test-2/

Any help will be really appreciate, thank you.