Looking at the code, it is using a script from Browser Update[1] to determine whether to show that message.

Here's the line from the js you linked to that checks the browser version:

    window.checkBrowserVersion = function() { i()({ required: { i: 12, e: -4, f: -3, o: -3, s: -1, c: -3 }, insecure: !0, unsupported: !0, reminder: 0, reminderClosed: 168, style: "corner", api: 2019.06, test: !1, onshow: function() { window.track && window.track("BrowserUpdate", "outdated_version_dialog", "Browser version outdated dialog") } }) }, $((function() { window.checkBrowserVersion() }));

The c: -3 is the crucial bit that should cause it to trigger if your version is at least 3 versions out of date.

Yours isn't though. Can you access http://browser-update.org ? If not, then there might be something with your DNS settings. Have you tried tethering through your phone? Have you changed your user agent?

1. http://browser-update.org/#install