Blank or white pages on your site indicate an issue with your server directly and you should contact your hosting provider for assistance. Possible causes:
1. Your back end server is returning a 500 internal server error.
2. A caching plugin or extension for your site is causing a conflict.
If you want to see if its your server that is having an error (without the influence of Cloudflare in between), you can use cURL to check this article: How do I check my server's response directly without Cloudflare