My callback URL is just a blank page

So I’m missing something. Here is the process I went through:

1. Downloaded and installed the plugin
2. Went to the twitter dev website and created my app and changed the permissions to read and write.
3. Obtained and added the twitter consumer and consumer secret key.
4. Uploaded my file and created my pay button.
5. Created my initial landing page to insert the button, then published it.
6. When I click on the button, it gives me an “Unauthorized 401” error.
7. Went to the Pay With A Tweet actual website.
8. Created a button there and activated a campaign.
9. Everything worked (posts to twitter/facebook, all the directions ultra clear and easy to work with) until I got to the file download page (callback URL).
10. Callback URL is a blank page.

I tried creating a page for the callback URL, but I can’t. How do I create the callback URL page and design it so this can go live? In one post, I read that there needs to be a friendly setting? How do I do that? In the dev.twitter my apps section, I’m not seeing anything to change from the “default” setting. My callback URL was created by the plugin, but I can’t edit the page. I know I’m missing something very important here. Help would be appreciated. Thank you very much in advance! 🙂

https://wordpress.org/plugins/pay-with-a-tweet/