Letsencrypt does not find A records for my domain, DNSSEC issue?

Hi all,

Im running a couple of virtual hosts on my droplet. I have secured 1 of them successfully with letsencrypt. When I try to secure a second one I run into trouble, I get the following error:

IMPORTANT NOTES:
 - The following errors were reported by the server:

   Domain: www.mini-paradise.com
   Type:   None
   Detail: DNS problem: SERVFAIL looking up A for
   www.mini-paradise.com

Also when running letsdebug I get DNS lookup errors. (https://letsdebug.net/mini-paradise.com/75799) I’ve configured both domains with the same DNS entries. The first domain works but this one doesn’t.

This is my DNS zone as set up in digital ocean control panel:

$ORIGIN mini-paradise.com.
$TTL 1800
mini-paradise.com. IN SOA ns1.digitalocean.com. hostmaster.mini-paradise.com. 1572985497 10800 3600 604800 1800
mini-paradise.com. 1800 IN NS ns1.digitalocean.com.
mini-paradise.com. 1800 IN NS ns2.digitalocean.com.
mini-paradise.com. 1800 IN NS ns3.digitalocean.com.
mini-paradise.com. 3600 IN A 167.99.221.33
www.mini-paradise.com. 43200 IN CNAME mini-paradise.com.
mini-paradise.com. 3600 IN CAA 0 issuewild "letsencrypt.org"

The website runs successfully under HTTP, and is reachable.

WHOIS lookup does show that the nameservers are successfully set to digital ocean: https://www.transip.nl/whois/prm/mini-paradise.com

I did some DNSSEC checks and I see some errors, but I have no idea what they mean how to resolve them: https://dnsviz.net/d/mini-paradise.com/dnssec/

Any suggestions are very welcome.