Let's Encrypt certificate keeps failing on Synology NAS

Help
1

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.

My domain is:

I ran this command:
I am using the synology control panel not command prompt

It produced this output:
The process has failed. Please login to DSM again.

My web server is (include version):
Synology DS1522+

The operating system my web server runs on is (include version):
DSM 7.2.2-72806 Update 9

My hosting provider, if applicable, is: Synology

I can login to a root shell on my machine (yes or no, or I don't know):
I don't know

I'm using a control panel to manage my site (no, or provide the name and version of the control panel): No

I have opened the necessary ports (80, 443, 5001) I have checked using Open Port Check Tool - Test Port Forwarding on Your Router to confirm the ports are in fact open. I have run my domain through https://letsdebug.net/ and it says everything looks good. I am unsure of how else to proceed.

The how to guide I am using is here Synology: How to Add Wildcard Certificate – Marius Hosting

2

Would you explain more about the error you are getting?

Because you have gotten 13 wildcard certs in the past 90 days. Some as recent as today.

Note that ports 80 and 443 are not used by Let's Encrypt when issuing a wildcard cert. Those are only used for an HTTP Challenge. A wildcard cert must use the dns-01 challenge which uses the public DNS system to validate your request.

See: Certificate Transparency search with grouped results | CertObserver

Further, tests to that domain using HTTPS work and are using a cert from today

Subject: CN=rapidresponse.synology.me
Issuer: C=US, O=Let's Encrypt, CN=YE1
Validity
    Not Before: Jul 16 20:23:57 2026 GMT
    Not After : Oct 14 20:23:56 2026 GMT

Cert type: ECDSA
Signature Algorithm: ecdsa-with-SHA384
Public Key Algorithm: id-ecPublicKey
    Public-Key: (256 bit)
    ASN1 OID: prime256v1
    NIST CURVE: P-256

X509v3 Subject Alternative Name: 
    DNS: *.rapidresponse.synology.me
    DNS: rapidresponse.synology.me
3

Everytime I have tried to replace the certificate I get a pop up and all it says is "Process Failed. Please sign in to DSM and try again." When I check the current certificate within the control panel it still isn't the Let's Encrypt certificate. I guess it is sending the request properly but my server is not receiving the certificate once it is issued.

4

HTTPS requests to your domain are working fine: SSL Server Test: rapidresponse.synology.me (Powered by Qualys SSL Labs)

That might be something better asked at the Synology forum or support. As noted, you are getting many Let's Encrypt certs and your server is using them. The Synology people will know better why their panel is showing you those results.

5

Will do thank you for your help

6

Go to Control Panel -> Security -> Certificates, then click "Settings". In the "Configure" tab you'll be able to select which certificate is used for which service. I think you need to change "system default" for the DSM UI.

Note: I'm not using DSM in English, so the translated names may be slightly different for you.