timestamp missing in source

Hi, I’m running into a strange issue. I believe my cache is working correctly, but I’m not able to see the nginx helper timestamp when I view the source. Interestingly, if I ftp into the cache directory, I am able to view the cached files in notepad++ and the timestamp text is there. It just fails to be written inside the browser when selecting view source. Any ideas?

https://ww.wp.xz.cn/plugins/nginx-helper/