Embedded browser, signin-container empty

We are a 3rd party application provider. Our application provides an HTML login pane for integrating with web services. One of those web services (ShareFile) supports SSO via Okta.

The initial URL we are attempting to hit: https://wipflifinancialadvisors.sharefile.com/saml/login

When we view the page in Chrome, it displays the username and password fields fine.

When we view the login page in our embedded browser, the Okta header and footer appear, but the login fields don’t appear.

There is a element with two hidden input fields, and there is a ‘signin-container’ div, but it is empty. We just aren’t seeing the login screen/fields themselves.

Our embedded browser uses JavaFX’s WebEngine component.
We set the user agent to “Chrome/60.0.3112.113”.
Javascript is definitely enabled.

Does anyone have any pointers?

bumping - I really hope that someone will have some ideas…