Expires Headers not Being Recognized

Hello @crowe

Thank you for your question and I am happy to assist you with this.
As in the gzip topic you opened and the test performed on gtmetrix, the performance of your website is great. Pingdom does not offer a detailed explanation on which files do not have cache control.
However, as gtmetrix suggest some files have 7 days cache TTL instead of the recommended 1 year:
https://americancatholichistory.org/wp-content/cache/minify/0c95c.js
https://americancatholichistory.org/wp-content/cache/minify/52dce.css
https://americancatholichistory.org/wp-content/cache/minify/d9164.css
https://americancatholichistory.org/wp-content/cache/minify/fb4e2.js
https://americancatholichistory.org/wp-content/cache/minify/584b6.js

Since your website is served from Cloudflare, the reason for this is that you need to change the Browser Cache TTL in the Cloudflare configuration to respect existing headers (the headers set by W3 Total Cache in Performance>Browser Cache)

Thanks!