Nginx – Receiving a 404 for a file that exists in nginx web server

I recently switched the web server on my CentOS 7 machine from Apache to nginx. I use software to take screenshots on my computers and to upload them to the server for public viewing. Originally, it worked fine on Apache – however, now I am running into an issue where nginx will serve a 404 error for some of my .png images on the web server.

I referred to this question with a very similar issue, but I couldn't make sense of the solution in the context of my own problem.

I have a snippet of the server block for the image server below.

server {
    listen       80;
    server_name  imageserver.example.com;
    root         /usr/share/nginx/imageserver.example.com/public_html;

    access_log   imageserver.example.com/logs/imageserver.example.com_access.log;
    error_log    imageserver.example.com/logs/imageserver.example.com_error.log crit;

    location / {
        index  index.html index.htm;
    }

    location ~* \.png {
        root       imageserver.example.com/public_html/u/;
        expires    max;
        add_header Pragma public;
        add_header Cache-control "public, must revalidate, proxy-revalidate";
    }
}

An example link is this image. I have confirmed the file exists on the server, and it has the following permissions.


$ lsa 7b724394b851299c68b15f1172f158c6.png
-rw-rw-r--. 1 jflory nginx 2.4K Nov 3 11:13 7b724394b851299c68b15f1172f158c6.png


I am very confused about how to fix this. What could the problem be?