OAuth login over custom domain gives blank screen in hybrid app

I am working on a hybrid phonegap package for Android and am running in some issues with the login procedure.
We use OAuth authentication on a Microsoft Azure environment ('regular', not SAML). I adjusted the index.html of the package to make sure the login procedure starts in the InAppBrowser. This works for the standard Mendix app-url, but fails for the custom domain we implemented. Instead of the landing page of Azure the app's screen stays blank. Anybody know what I need to set or do to get an https request across the ustom domain?