Trouble connecting to Let's Encrypt from Synology DS218play

Hi. I have been trying to get a Let’s Encrypt SSL Cert for my Synology DS218play NAS as their Cert is failing as not from a trusted source. Well, when I enter my domain and email to apply for the cert it fails to connect to Let’s Encrypt and queries the domain. What should I do? Can you issue me a cert? Can I send you a CSR? Thanks in advance, Níall


Whats the detailed error message?
What failed? (Connection from your NAS to let's encrypt ? or vise versa?)

You'll need to do that by yourself. We can't help you obtain a certificate without proper validation from your domain.


Thank you

Whats the detailed error message?
What failed? (Connection from your NAS to let’s encrypt ? or vise versa?)

AquaDome: Message is Unable to connect to Let’s Encrypt. Domain name not valid. - When trying to connect from NAS to Let’s Encrypt.

Hi @AquaDome

and what's your domain name? You must have a public visible domain name if you want to get a Letsencrypt certificate.

Perhaps there are some settings that I have overlooked on the NAS which need to be adjusted?

Our Domain name is:

Is this the domain name of your Synology DS218play NAS?

There - - is a self signed certificate:


I had tried a self signed cert thinking that might suffice but that didn’t pass either. I have now reverted to the original cert from but cannot connect to Let’s Encrypt. Error message: Cannot connect to Let’s Encrypt. Check that the Domain name is valid. What Domain name should be in the request? Am I missing something? is our website domain. The NAS is on our network. What is the NAS domain? Do I need to join it to a domain? Please enlighten me. The exact error message I’m getting is: Failed to connect to Let’s Encrypt. Please make sure the domain name is valid.

A lot of Synology things have integrated solutions. Normally, these should work.


sounds that your Synology DS218play can't connect to a server outside.

Is there a firewall which blocks outgoing connections? You need a domain name like

with an A-record -> your Synology DS218play public ip address.

The Synology DS218play tries to connect Letsencrypt, creates a new order, validates the ownership of, then gets the certificate.

Your error message looks like outgoing connections are not allowed.

Also, there's no public accessible IP address assigned to this hostname.

Thank you

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