Argument 1 of Node.appendChild is not an object.

[lol768]

Look:

rxp-js/dist/rxp-js.js

Lines 221 to 229 in 4fd6948

	if (spinner.parentNode) {
	spinner.parentNode.removeChild(spinner);
	}
	closeButton = internal.createCloseButton();
	overlayElement.appendChild(closeButton);
	closeButton.addEventListener("click", function () {
	internal.closeModal(closeButton, iFrame, spinner, overlayElement);
	}, true);

Hmm, when can closeButton be undefined?

rxp-js/dist/rxp-js.js

Lines 100 to 103 in 4fd6948

	createCloseButton: function (overlayElement) {
	if (document.getElementById("rxp-frame-close-" + randomId) !== null) {
	return;
	}

Maybe every single time after the initial load when the iframe navigates to a URL? Which .. happens every single time the user is 3DS-challenged?

Come on, did you even test this code?