IDEA 2018.3.1 －Unable to get network connection when trying to install plugins

Please check your IDE proxy settings. Also, your ISP may be blocking access to https://plugins.jetbrains.com/ site. Make sure you can open it.

Do you use the same proxy in the browser?

I am sure I am using the same proxy

I am wondering why the previous version （2018.3） is working well，Other than that, I haven't  changed any settings ， can u find a solution from the log?

Your proxy server or local firewall is blocking the connection.

I am sure I can access to https://plugins.jetbrains.com/ , Also, the proxy is working well after the rollback (to 2018.3),  

Local firewall can block specific apps. IntelliJ IDEA app may be blocked while your browser is not.

You mean version 2018.3.1 may be blocked， but  version 2018.3 not ?

Yes, local firewalls can block specific apps/versions.

Contact your network admin/ISP for help.

OK, thanks for your advice.

This problem has been solved，thanks for your information and help!   ~~~^_^~~~

My network admin/ISP intercepted the request.

I had the same problem when I installed another SDK after the initial install of Android Studio(AS). Apparently, AS got confused as to which version I was searching plugins for, and gave up. So, I got empty window when I tried to search for a plugin. After deleting that extra SDK, I got the plugin search function back to normal. Thought to share this experience. I'm a newbie to Android. I thought installing an extra SDK may help mitigate some compatibility issues. Dumb! AS (version 3.5) will have SDK version 10 installed automatically when AS was first installed. But if you try to create a virtual device, it will ask you to install an ABI. If you try to install any ABIs listed under version 10 of the SDK, it will tell you they are NOT available. You could then go to install an ABI of an older version. It will be OK. If you think it may be better if you also install the matching SDK, and end up with 2 versions of the SDK in your system, you get into the trap I was in. So, to cut the story short, NEVER INSTALL TWO VERSIONS OF SDK IN ONE SYSTEM!

Ctrl + Alt + s, HTTP Proxy Setting, Auto-detect proxy settings and click OK