Most probably this error happened because Safari does not allow iFrame URLs to create cookies, that's why you see the white page. 

In this article you will be going to know about:

How to investigate the reason that caused this error?

You can check out this issue by receiving the 404 error message/screen in the iFrame page component in your Safari browser.

Reason #1: Previewing the iFrame mode in Safari browsers

This means that you are trying to use the iFrame mode (embed page) to display the PayTabs payment page using the Safari browser, in which case Safari does not support iFrame URLs to create cookies, that's why you see the empty/error page. 

Safari ships with a conservative cookie policy that limits cookie write to only the pages chosen ("navigated to") by the user. This default conservative policy may confuse frame-based sites that attempt to write cookies and fail.

You need to make a browser detection/checker in your code to see whether your client is using a Safari browser or not. If so then you will have to fully redirect your client in this case to the PayTabs payment page instead of using iFrame mode.