Two domains www.sheffieldweather.net and sheffieldweather.co.uk.
When I originally created the certficate in the synology under alternative names I forgot to add www.sheffieldweather.co.uk so I now get an warning that the site isn't secure.
www.sheffieldweather.net and sheffieldweather.net or sheffieldweather.co.uk all work fine with https
I tried creating a new certificate with www.sheffieldweather.net as the main host and as alternative names I have www.sheffieldweather.co.uk; sheffieldweather.co.uk; sheffieldweather.net and it fails with invalid domain when running the check
If I create a certificate with just www.sheffieldweather.co.uk as the main host I get a certificate issued.
Is it failing as I've already got a valid certificate for the other names and therefore can't add them again? Or am I missing something else?
Welcome to the Let's Encrypt Community! 
Are all four of these domain names supposed to be aliases for serving the same content? It's advisable to only cover domain names with the same certificate if they are intended to be aliases for serving the same content.
www.sheffieldweather.co.uk, sheffieldweather.co.uk, and www.sheffieldweather.net are all serving a certificate that only covers sheffieldweather.co.uk and www.sheffieldweather.net.
sheffieldweather.net is unreachable.
Hi. Just checked sheffieldweather.net and it is reachable at the moment.
The sites all serving the same content from the same folder.
I have fixed ip address so I'm not using ddns. There's no ipv6 connectivity as it's too much of a balls ache to sort out.
Originally the expired certficate covered all domains and the variations but failed to renew. So I recreated it but in error left out www.sheffieldweather.co.uk when I created it.
So if you type in https://www.sheffieldweather. co.uk you get a certificate error.
Earlier on when using nslookup I was getting a dns error whether I was connected to my own network or another one. I'm not getting that now. No idea if that was part of the issue or not.
Hello @lostwithssl,
Using the online tool Let's Debug yields these results.
https://letsdebug.net/sheffieldweather.net/2969528
And from around the world DNS results are here Permanent link to this check repor
All saying "Not found".
Mmm looks like I need to contact my domain manager. It should be there.
The setting are the same for sheffieldweather.co.uk
Looked at the dns zone file and there is a differance between the two. www.sheffieldweather.co.uk has an A record with the ip address as well while www.sheffieldweather.net only has an A record for the host name.
Sadly I can't see a way to edit or add the record so raised a ticket.
At this point I suggest using Let's Debug on each of the FQDNs you have that actually have an IP Address (either or both IPv4 A Records, IPv6 AAAA Records) and
The create a certificate with only those FQDNs that have an IP Address.
Hopefully that will get you going while working on fixing those FQDNs that currently DO NOT have an IP Address.
Now backup and running properly. Funny how I managed to get a certificate for sheffieldweather.net before though. I hadn't changed anything from the time I created it.
