There is some JavaScript located inside one of the ecommerce module templates that is redirecting your users away. The intent of that script is to make it so your users don't remain on the secure domain ( after leaving that page. However, you have to change the non-secure domain referenced in the script to your client's domain.

For example, in the Charity template the script looks like this:

<script type="text/javascript">
$(function () {
// redirect to non-secure version of page
    $("a").each(function (idx) {
        var href = $(this).attr("href");
        if (href.indexOf("http") == -1 && href.indexOf("https") == -1) {
            href = ""; + href;
            $(this).attr("href", href);

Where it says,, you would change it to your client's domain.

The layout template can be found in the admin in the following location (square brackets indicate a button to click):

[Site Manager][Module Templates][Online Shop Layouts][Registration - Buy]