Cert is due for renewal, auto-renewing...
Renewing an existing certificate
Performing the following challenges:
tls-sni-01 challenge for manage.stage.nowbackto.me
Waiting for verification...
Cleaning up challenges
Attempting to renew cert (manage.stage.nowbackto.me) from /etc/letsencrypt/renewal/manage.stage.nowbackto.me.conf produced an unexpected error: Failed authorization procedure. manage.stage.nowbackto.me (tls-sni-01): urn:acme:error:dns :: DNS problem: NXDOMAIN looking up A for manage.stage.nowbackto.me. Skipping.
All renewal attempts failed. The following certs could not be renewed:
/etc/letsencrypt/live/manage.stage.nowbackto.me/fullchain.pem (failure)
1 renew failure(s), 0 parse failure(s)
Are there particular configuration files I should be editing and with what? I've seen similar posts on here using dig but I'm not sure what to use there.
When using this method, the hostname has to actually exist in DNS. But this hostname doesn’t exist in DNS. (If you can still access the site from your own machine, you may have hardcoded it in your hosts file?)
As an update, I ran whois nowbackto.me and I found out that your domain has expired at the registrar, Namecheap, which would also explain why all of the associated DNS records are now missing! You would have to pay Namecheap a renewal fee and possibly a late-payment fee in order to recover use of this domain.