Hi Sadegh,
Thanks for the screenshot... it seems that there is some connection issue with Chrome and your machine (network probably)... I have seen other Chrome users complaining in Chrome forum about connection problem when they use it on Windows 10... Do you happen to have a Windows 10 machine? Is it a 64-bit OS? Are you using proxy server?
I think your published file is fine as I have no problem to preview it on a Mac and a Windows 8 laptop on our end, so one thing we could try is to make sure you have 64-bit Chrome installed and Google Web Designer updated to 1.6.0.0429 (the latest version that we just released this week).
If you do have a Win 10 64-bit OS machine, would you please try the following steps:
1) Uninstall Chrome
2) Download 64-bit Chrome installer from Google and install it
3) Launch 64-bit Chrome
4) Open GWD - check "Help > About GWD" to see if it is updated to 1.6.0.0429
5) Open the file you were working on before
6) Preview in Chrome
Or 5) Create a new file, add a youtube component and preview in Chrome
Hope this works for you.
Thanks,
Emily (GWD Team)