Your account credentials have been saved in your Certbot
configuration directory at /etc/letsencrypt. You should make a
secure backup of this folder now. This configuration directory will
also contain certificates and private keys obtained by Certbot so
making regular backups of this folder is ideal.
A private, inaccessible, IANA/IETF-reserved IP address was found for chess-calculator.com. Let's Encrypt will always fail HTTP validation for any domain that is pointing to an address that is not routable on the internet. You should either remove this address and replace it with a public one or use the DNS validation method instead.
192.168.1.131
Since Let's Encrypt isn't inside your LAN, it can't connect to your web server to validate that you actually control the domain. You can read more about the HTTP challenge here: Challenge Types - Let's Encrypt
If you want to be able to issue a certificate this way, and for your website to be available to visitors outside of your LAN, you need to make your website available on a public IP address.
192.168.1.131
Warning: Private ip address found. No connection possible. There are two types of ip addresses: Worldwide unique, global addresses and private addresses. If you want that other users connect your domain, your domain must have minimal one A- (ipv4) or AAAA- (ipv6) entry with a global ip address. Check Private network - Wikipedia to understand the details: 192.168.0.0 to 192.168.255.255: Class C - 256 private net, every with 256 addresses