I noticed that iThemes Security does not play nice with WP Super Cache.
Cache Tester
Test your cached website by clicking the test button below.
Fetching http://www.website.com/ to prime cache: OK
Fetching first copy of http://www.website.com/: OK (1.html)
Fetching second copy of http://www.website.com/: OK (2.html)
One or more page requests failed:
Page 1: 403 (Forbidden)
Page 2: 403 (Forbidden)
The pages do not match! Timestamps differ or were not found!
https://ww.wp.xz.cn/plugins/better-wp-security/