Can't get extension

I cannot get an online extension (and even a list of extensions) from VS 2013 Professional.

The HTTP request to https://visualstudiogallery.msdn.microsoft.com/services/dev12/extension.svc 'has exceeded a valid timeout.

But I can open https://visualstudiogallery.msdn.microsoft.com/services/dev12/extension.svc in a browser on the same computer.

I disabled the firewall but it doesn't help. How can I fix this?