Hello,
Some news after a lot of investigation.
I enabled the "DebugMode" in the plugin for another website would reported the same issue.
I was able to see that there is a 404 page returned by MangoPay during the OAuth authentication call.
The return content is a HTML page
<title>Error Page</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<link rel="stylesheet" type="text/css" href="/Content/themes/barnie/css/bootstrap.min.css">
<link rel="shortcut icon" href="/Content/themes/barnie/img/custom/favicon.png">
<style type="text/css">
body {background: #f7f7f7 url(/Content/themes/barnie/img/main-back.png) repeat;text-align: center;}
div {margin-top: 50px;}
div.title {font-size: 5em;font-weight: bold;}
div.message {font-size: 2em;}
</style>
<div class="logo">
<img src="/Content/themes/barnie/img/custom/logo.png">
</div>
<div class="title">:-(</div>
<div class="message">Oops, that page can not be found.</div>
I made a little search on "barnie/img/main-back" and I have found that the page is a 404 page coming from MangoPay :
github.com/Mangopay/mangopay2-java-sdk/i...suecomment-525256369
The MangoPay plugin is not using the latest version of the PHP Library provided by MangoPay but that library should be still supported by the platform.
For an unknown reason, something changed in the MangoPay API platform and, in some websites, the OAuth called return with that 404 page (I can't reproduce it in two test websites, using different PHP version, etc).
ManogPay support is telling that they do not receive any API call from the website but. The call is perform and catch by "something" which gave that 404 HTML page instead.
The plugin is performing the cURL call as before ; the fact that they server do have a "firewall" (or something else), blocking content is not the plugin fault (since it's using their official library and it is working on some websites).
I do hope that their support will be able to perform a full investigation and perform a fix on their platform ; which seem to be a important regression impacting multiple website.
But I do understand that it's easier to reply on the plugin fault
Testing the issue is simple ; it requires to edit the "plugins/hikashoppayment/mangopay/mangopay.php" file and replace the line
$this->api->Config->ClientPassword = $this->params->get('clientpassword');
By
$this->api->Config->ClientPassword = $this->params->get('clientpassword');
$this->api->Config->DebugMode = true;
And then, in the HikaShop backend, edit the MangoPay payment instance and click on "save".
Some debug data will be printed on screen, generated by the MangoPay PHP Library and if you see the smiley with the content "Oops, that page can not be found.", you got the MangoPay 404 page.
Regards,