Please fill out the fields below so we can help you better. Note: you must provide your domain name to get help. Domain names for issued certificates are all made public in Certificate Transparency logs (e.g. https://crt.sh/?q=example.com), so withholding your domain name here does not increase secrecy, but only makes it harder for us to provide help.
Looking at the hostname, you're using a Synology product. Most Synology products with the capability to get a (Let's Encrypt) certificate can renew those certificates automatically.
However, for that to work, the Let's Encrypt validation server needs to be able to connect to your Synology products (unless it's using a DNS plugin for validation, but I'm not aware Synology products have that capability). Unfortunately, I am unable to connect to your hostname on port 80 (HTTP). And if I can't connect, chances are the Let's Encrypt validation server can't connect too.
Therefore I recommend you check if the Synology product hosting your website is accessible from the outside (i.e., the "world wide web"). Perhaps a firewall setting or a router portmap needs to be opened.
Why?!? 
