which key??

[simpsonetti]

When i type this here at command prompt:
ntfy serve
i get this:
yaml: line 21: did not find expected key

In line 21 there is only a #

19 # To listen on all interfaces, you may omit the IP address, e.g. ":443".
20 # To disable HTTP, set "listen-http" to "-".
21 #
22 listen-http: ":80"
23 listen-https: ":443"
24
25 # Listen on a Unix socket, e.g. /var/lib/ntfy/ntfy.sock
26 # This can be useful to avoid port issues on local systems, and to simplify permissions.
27 #
28 # listen-unix:
29 # listen-unix-mode: <linux permissions, e.g. 0700>
30
31 # Path to the private key & cert file for the HTTPS web server. Not used if "listen-https" is not set.
32 #
33 key-file: "/home/rzadmin/cert/ntfy.key"
34 cert-file: "/home/rzadmin/cert/ntfy.crt"
35

so which key does is mean?
Thanks and regards