System Proxy Settings not working after updating to El Capitan(10.11.1)

Question

I am usually using internet through proxy and it was working great with Yosemite 10.10.5.

But yesterday I have updated OS to El Capitan 10.11.1 and now same proxy settings are not working anymore.

Strange thing is that its working only in Firefox, but in Firefox we have provided Proxy settings externally (I am not using System proxy settings in that).

Can any one please help me in this, I have tried many proxy application as well but its no help (such as Proxifier, Charlesproxy, Authoxy, Proxycap, Spotflux).

I am not getting any error, Only looks like my Mac is not connected with internet, But it is as its display connected state in Network setting for Ethernet, also proxy is working in Firefox if i set its proxy settings there.

Also my office has another 10 mac, in which 2 mac has 10.11.1, and other has 10.10.5. And only 10.11.1 Mac doe not able to connect with Proxy (works in Firefox again), have contact Apple but they are also not sure whats the issue.

Here is the screenshot for my Settings, Sorry for blur, cant disclose all settings ;).

And here is the screenshot of firefox, where i have added same proxy setting, and in firefox its working,

Also as i said, same settings work other 8 Mac which has Yoshemity.

Update
I am checking some tutorial on ATS.
And is it possible that it is due to ATS?

@Everett, here is the image you have asked, Also safari display this message immediately, not waiting for anything.

Solution

Got the issue solved from this link.

Advanced TCP/IP settings Set up some network services to use IPv6 addresses instead of IPv4 addresses. See Adjust advanced TCP/IP settings.

Till now we are only using IPV4, but when I have setup IPv6 then it's working.

Now it looks like this:

Comments

[Admin]

@kenorb, thats the issue, I am not getting any error, Only looks like my mac is not connected with internet, But it is as its display connected state in Network setting for Ethernet, also proxy is working in Firefox if i set its proxy settings there.

[Admin]

Also my office has another 10 mac, in which 2 mac has 10.11.1, and other has 10.10.5. And only 10.11.1 Mac doe not able to connect with Proxy(works in firefox again), have contact Apple but they are also not sure whats the issue.

[Admin]

@kenorb added the screenshot, also has added screenshot for Firefox.

[Admin]

@kenorb can you please check my update, Could it be bcoz of ATS?

[Admin]

What shows up in the console when you are trying to connect? I am guessing that you are potentially running in to a timeout. I'm willing to bet the amount of time FireFox is waiting is higher than the amount of time Safari is waiting, so FireFox gets the connection, and Safari does not. Start with your settings as they are expected to work, open console, then open safari and see if you get any error messages in the console.

[Admin]

Yes Safari also not able to connect to internet, i have added screenshot, also i have added it as question in developer forum here,discussions.apple.com/thread/7390904