API signature error

I have installed this plug in today and set up an Apple News publisher account. Trying to publish three pieces (as per Apple News instructions) in preview mode so they can approve my account. It’s not working and this is the error I’m getting:

API: WRONG_SIGNATURE

I’ve contacted Alley Interactive for support and they cannot help. Has anyone experiences this and knows how to fix it?

My wordpress site is hosted by Fresh Sites. Could it be a problem with my host?

Here is the debug information which I cannot make head not tail of as I am not a developer!

API Response:
Array
(
[headers] => Requests_Utility_CaseInsensitiveDictionary Object
(
[data:protected] => Array
(
[request-id] => 3cba7bc0-1253-11e8-ac6a-c76f6a840487
[www-authenticate] => HHMAC
[content-type] => application/json;charset=UTF-8
[content-length] => 39
)

)

[body] => {“errors”:[{“code”:”WRONG_SIGNATURE”}]}
[response] => Array
(
[code] => 401
[message] => Unauthorized
)

[cookies] => Array
(
)

[filename] =>
[http_response] => WP_HTTP_Requests_Response Object
(
[response:protected] => Requests_Response Object
(
[body] => {"errors":[{"code":"WRONG_SIGNATURE"}]}
[raw] => HTTP/1.1 401 Unauthorized
Request-Id: 3cba7bc0-1253-11e8-ac6a-c76f6a840487
WWW-Authenticate: HHMAC
Content-Type: application/json;charset=UTF-8
Content-Length: 39

{"errors":[{"code":"WRONG_SIGNATURE"}]}
[headers] => Requests_Response_Headers Object
(
[data:protected] => Array
(
[request-id] => Array
(
[0] => 3cba7bc0-1253-11e8-ac6a-c76f6a840487
)

[www-authenticate] => Array
(
[0] => HHMAC
)

[content-type] => Array
(
[0] => application/json;charset=UTF-8
)

[content-length] => Array
(
[0] => 39
)

)

)

[status_code] => 401
[protocol_version] => 1.1
[success] =>
[redirects] => 0
[url] => https://news-api.apple.com/channels/0bade538-4ae3-4e71-bd3e-e8141fe919c7/articles
[history] => Array
(
)

[cookies] => Requests_Cookie_Jar Object
(
[cookies:protected] => Array
(
)

)

)

[filename:protected] =>
[data] =>
[headers] =>
[status] =>
)

)

Request Meta:

Array
(
[data] => Array
(
[isPreview] => 1
[maturityRating] => GENERAL
)

)

The page I need help with: [log in to see the link]