JSON loading iOS error: NSURLConnection HTTP load failed

General
1

Hey,
I’m getting an error in iOS (10.2.1) in a Fuse project when fetching an https:// url.
Fetch:

    fetch('https://s3.amazonaws.com/MYJSONFILE.json')
        .then(function(response) {
          return response.json();
         })
        .then(function(responseObject) {
          resolve(responseObject);
         });
       });

XCode output:

2017-07-14 14:13:31.463348+0100 json[648:107898] [] nw_coretls_callback_handshake_message_block_invoke_3 tls_handshake_continue: [-9807]
2017-07-14 14:13:31.464215+0100 json[648:107909] NSURLSession/NSURLConnection HTTP load failed (kCFStreamErrorDomainSSL, -9843)

I believe it’s something to do with App Transport Security Settings, but they are set as recommended on SO: https://stackoverflow.com/questions/43847836/swift-3-nsurlsession-nsurlconnection-http-load-failed-when-connecting-to-a-site?noredirect=1&lq=1

Any clues?
Thanks!