Synology - Let's Encrypt is unable to validate this domain name

My domain is:


I don't have a website, I'm trying to set up a Reverse Proxy on my Synology DS920, I did this only last week, I had a few issues with the above error but finally got the certificate installed when I'd got the notation correct, and CName's all setup, being one example

Sadly, by NAS died on Tuesday following a power outage during a RAID rebuild after a drive replacement, then DSM reinstalled itself and the last system config backup was before I'd configured the certificate and reverse proxy! So i've lost that certificate

I'm getting this error again and my router firewall config hasn't changed, but before I troubleshoot any further, I just wanted to rule out a note on the setup wizard that according to Lets Encrypt policies the number of email addresses for certificate registration and the number of certificate requests for a domain are both limited...... Could this be my issue, since I only did it last week?

Thanks in advance,

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Not from where I'm sitting. shows only two certs ever having been issued; And both are more than one week old: |
So you are definitely good to go for a new cert.

P.S. Sorry to hear about your power/drive failures :frowning:
You may have lost some time, but you haven't lost your mind!
You only need to repeat your steps and resolve this problem (like before) :slight_smile:

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Thanks @rg305 for confirming this, I appreciate the quick response, I'll get back to prodding it with my thinking stick!

Also appreciate your kind words, I nearly lost my mind when I lost 11TB of data, but thankfully, the memories were backed up!


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@rg305 I was thinking this morning, is it possible for me to download the certificate I created on the 21st, so I can just import it manually, rather than creating a new one? Seems a shame to duplicate...


Only if you still have the private key for it.
Certificates are public information; And without their private key, they are incomplete.
There is nowhere to download the private key from.
Since you lost the data on that drive (including the private key), you must now issue a new cert/key pair.

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Thanks @rg305, certificates really aren't my strong point! However, I found a typo in one of my CNames, and have now successfully created a new ticket. Thanks for your help

You're very welcomed :slight_smile:

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