Blank or white pages on your site indicate an issue with your server directly. Therefore, 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 whether that your server is having an error (without the influence of Cloudflare in between), you can use cURL to check.