Did you figure this out?
I would be interested as well, we have been getting the same error and we have a HTTP proxy defined.
No, i didn't solve this.. yet.
Think this is a bug in the code thats calling the addon store over https.
"System.Net does not support https connections to a proxy server. We will tunnel an https request through a proxy to the destination host, but will not connect via SSL to a proxy server.
I have not looked into the actual problem with proxies and HTTPS but I wanted to make sure that you have read the information that you can now install and manage add-ons from Visual Studio: http://world.episerver.com/articles/Items/2-important-improvements-for-managing-addons-in-episerver/. Though we still support installation of most add-ons through the user interface, our gut feeling is that most developers want to control the add-ons as regular Nuget packages, at least for production environments.
The only solution seems to be bypassing the proxy, allowing the server to communicate directly with internet through its default gateway. This is not a desirable solution at all and it's lowering the security a lot on the webservers. It's a shame it has to be this way when the rest of EPiServer works through proxy.
How on earth do i configure my proxy in s a way that addons-manager works? We have about 14 sites with the same proxy settings, and everything works great, exept addons.
The error i get is this:
Exception details: NotSupportedException: The ServicePointManager does not support proxies with the https scheme.
The config is as simple as this:
The site itself communicates just fine via proxy, eg. for retreiving RSS.