Error "Install Required Plugins"

Hello,

When I try to install this plugins

1 – Physcode – Visual Composer Addon
2 – Travel booking
3 – Visual Composer
4 – Revolution Slider

I got the following error:

Downloading installation package from http://physcode.com/plugins/revslider.zip…
Download failed. cURL error 7:

Please kindly advise how to fix this problem.

Best Regards,
Borin