I'm using Intellij IDEA Ultimate 2016.3.4.
File / Settings / Plugins / Install JetBrains plugin... opens up a window named Browse JetBrains Plugins, but the main area of the window, which should AFAIK list the plugins available on the JetBrains repository, only displays a "Nothing to show" message.
I am behind a corporate proxy, so I used the HTTP Proxy Settings... button & dialog box to configure proxy settings. I also used the Check connection button to test the proxy configuration with http://plugins.jetbrains.com/, and it worked fine. The Browse JetBrains Plugins window still remains empty. (I also tried the Reload button.)
Am I getting something wrong?
(Yes, I also know there's a workaround: I can download the plugin, and install it manually. The question is not about the workaround, but the in-application download & install feature.)
Based on the comment of y.bedrov, I looked at idea.log, and found several instances of the same SSL certificate related exception:
sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
This error can be reproduced using the Check connection button described above, the important thing is to use https in the URL (e.g. https://plugins.jetbrains.com/).
So this looks like a classic SSL certificate path problem. The tricky part is that the web proxy used touches the certificate chains and replaces the original root certificate with the company's own web proxy certificate. The latter is apparently not trusted by the JVM, so it looks like the solution is to export the web proxy root certificate to a file, then import it into cacerts. This solution is described in several existing blog posts (here's an example, a simple Google search may yield dozens more).