I use OpenVPN in my Ubuntu. I can access every site, except YouTube, Facebook, and Twitter. Chromium says that the site cannot be reached, that it took too long to connect.
I tested this in other systems running Lubuntu, but I have the same problem. I also tested on Windows to see if this happens there when using OpenVPN, and this does not happen.
What could be causing this issue, and how do I resolve the issue?