(Help) [cURL error 56: Receive]Error Installing Extension (WordPress, Jevelin theme)

I'm get this error when try to install Plugins & Extensions on this theme (Jevelin)
[I'm already changed the "Server to server" > External access without restrictions. But DON'T SOLVE THE PROBLEM!
HELP??

the error's:

Downloading the "Shortcodes" extension...

Failed to access Github repository "ThemeFuse/Unyson-Shortcodes-Extension" releases. (cURL error 56: Received HTTP code 403 from proxy after CONNECT)

Downloading the "Mega Menu" extension...

Failed to access Github repository "ThemeFuse/Unyson-MegaMenu-Extension" releases. (cURL error 56: Received HTTP code 403 from proxy after CONNECT)

Downloading the "Portfolio" extension...

Failed to access Github repository "ThemeFuse/Unyson-Portfolio-Extension" releases. (cURL error 56: Received HTTP code 403 from proxy after CONNECT)

Downloading the "Backup & Demo Content" extension...

Failed to access Github repository "ThemeFuse/Unyson-Backups-Extension" releases. (cURL error 56: Received HTTP code 403 from proxy after CONNECT)

Failed to access Github repository "ThemeFuse/Unyson-Shortcodes-Extension" releases. (cURL error 56: Received HTTP code 403 from proxy after CONNECT)

[alemoppo]

Hello, i can't find that theme in the themes list. Is it a theme that you bought elsewhere?

There are problems of theme activation with themeforest, because they don't accept requests with the User-Agent formed in a certain way. AlterVista instead for security reasons it always sends it in the format:

username.altervista.org/IP client (compatible; MSIE 7.0)

I don't know if this problem has been solved by themeforest.

Bye!