In your JS lib any version, but for example https://d35z3p2poghz10.cloudfront.net/ecwid-sdk/js/1.2.9/ecwid-app.js, you have a bug for getting the payload.
function getPayloadFromParam() {
var query = window.location.search.substring(1);
var vars = query.split('&');
for (var i = 0; i < vars.length; i++) {
var pair = vars[i].split('=');
if (decodeURIComponent(pair[0]) === 'devpayload') {
return decodePayload(decodeURIComponent(pair[1]));
}
}
return null;
}
where you are searching only for devpayload which is wrong because the request actually has payload query param.