To use HTTP validation, you need to add one or more relevant DNS records at your DNS provider (Dynadot, apparently).
caribsis.com has this A record, giving its IPv4 address:
caribsis.com. 10800 A 161.35.106.52
www.caribsis.com has no DNS records at all.
I don't use Dynadot, but it looks like they have documentation that shows how to add both records (including the one you already added, so you should be able to skip that step):
To quote it:
- In the "Subdomain Records (optional)" section, enter "www" as the subdomain, select "A" from the drop-down menu and then enter your IP address in the "IP Address or Target Host" box.