Https with Basic Auth failing on IOS only

Ionic Framework ionic-v3
1

Firstly, if you’ve encountered this problem before you may be thinking, add NSAppTransportSecurity, already done that, added in config.xml and even created a hook in after_prepare for it as follows:

#!/bin/bash

PLIST=platforms/ios/*/*-Info.plist

cat << EOF |
Add :NSAppTransportSecurity dict
Add :NSAppTransportSecurity:NSAllowsArbitraryLoads bool YES
EOF
while read line
do
    /usr/libexec/PlistBuddy -c "$line" $PLIST
done

true

It’s failing with this error:

{"_body":{"position":0,"totalSize":0},"status":0,"ok":false,"statusText":"","headers":{},"type":3,"url":null}

This is the code, same exact code works on Android and Web:

  let path = "https://us11.api.mailchimp.com/3.0/lists/xxx";
  let body = {"members": [{"email_address": email, "status": "subscribed"}], "update_existing": true};
  let headers = new Headers ({
    'Authorization': 'Basic T2xhOmNlN3R4N2I4MjQyMDg6UmU0MWQ0NDNiNjk2NTg1MjJjYHSzMTE='
  });
  let options = new RequestOptions({headers: headers});
  this.http.post(path, body, options)
    .map(res => res.json()).subscribe(data => {
       console.log(data);
    },
      err => {
       console.log(err);
    })

What could I be doing wrong please?

System:

cli packages: (/usr/local/lib/node_modules)

@ionic/cli-utils  : 1.9.2
ionic (Ionic CLI) : 3.9.2

global packages:

Cordova CLI : 7.0.1

local packages:

@ionic/app-scripts : 3.0.0
Cordova Platforms  : android 6.2.3 ios 4.4.0
Ionic Framework    : ionic-angular 3.7.1

System:

ios-sim : 5.0.8 
Node    : v6.10.2
npm     : 3.10.10 
OS      : macOS Sierra
Xcode   : Xcode 8.3.3 Build version 8E3004b
2

You could check for CORS Problems caused by WkWebView.