I've been attempting to secure my Synology and all the services I run with Let's Encrypt certificates and a reverse proxy. So I changed the A records, and AAAA records on my host's DNS settings and most of them work except for one specific domain and I have absolutely no idea why.
Some of the services are in Docker containers, others are just simply Synology DSM services. And all of them run fine, except on this specific domain. Namely dsm.desterradum.com, vault.desterradum.com, and vault-backup.desterradum.com.
The weirder thing is that I also got another domain name (dsm.theorderoflife.com) with exactly the same setting, routing to exactly the same Synology OS, which works perfectly fine. I'm not kidding, the DNS and routing settings are identical.
I keep getting the "Invalid Domain, please make sure this domain can be resolved into a public IP address" Error. Which is somewhat hilarious because when I go into my host's Plesk DNS page I can literally see a screenshot of the service loading so how would that possibly be there if the domain does not resolve?
According to https://dnschecker.org/ the domain resolves to the right IP address too on all DNS servers.
How can I solve this issue?
My domain is: dsm.desterradum.com
I ran this command: Get a let's encrypt certificate button
It produced this output: Invalid Domain Error.
My web server is (include version): Synology DSM 6.
The operating system my web server runs on is (include version): Synology DSM 6.
My hosting provider, if applicable, is: Some random Dutch webhost.
I can login to a root shell on my machine (yes or no, or I don't know): Yes perfectly fine.
I'm using a control panel to manage my site (no, or provide the name and version of the control panel): Plesk.