Why does http://example.com/.well-known/acme-challenge/test.html not show my file?

[mgutt]

I'm the Unraid template maintainer of the NPM docker container. To give better support I wanted to offer a method so users can check if Let's Encrypt is able to reach their domain to validate a certificate through the URL method.

At first I created a file as follows inside the NPM container:

echo "test" > /data/letsencrypt-acme-challenge/test.html
chmod 777 /data/letsencrypt-acme-challenge/test.html
chown 99:100 /data/letsencrypt-acme-challenge/test.html

I found the path in this nginx config.

After that I tried to load the html file, but I receive only a 404 error:

Why doesn't it load/display the html file?