If you've setup a Web Page step as part of your segment or channel and all you are seeing is a white screen, it means the website has placed security limits on how their page can be displayed. Some pages do not allow themselves to be inserted inside of another page.
How to Check
While viewing the channel, open up the chrome developers console. When the white screen loads instead of the page, check the console for errors. If there is an error that says Xframe options SAMEORIGIN, that is the issue.
Unfortunately, there is no way to display that particular page.