Hi,
Can you double check whether there is any Ad Blockers installed in your Chrome? Please disable it and try preview again (you may need to restart Chrome after disabling the Ad Blockers).
Also, do you have any special characters in your project file name? There is a known issue that preview would not work on Windows when the project file name contained character with accent.
If the problem still happens, can you open the console in Chrome (Right mouse click and select "Inspect" then go to Console tab) and look for any errors?
Thanks,
Emily
(Google Web Designer Team)