DNS problem: not resolving correctly; dig response includes "status: REFUSED"

I’ve got four domains, all of which I would like to point to a placeholder page (running on a LAMP droplet) while I develop my site.

Two of the domains are resolving properly, and two are not.

I’ve followed the steps in your DNS Tips and Tricks article (https://digitalocean.com/community/articles/dns-tips-and-tricks).

1. whois confirms that ns1, ns2, & ns3 at digital ocean are the name servers for all four domains

2. but dig shows that the two non-resolving domains are having some kind of issue, which I can’t decipher.

the GOOD domain includes this in the dig response:

;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 22718 ;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

whereas the BAD domain includes this in the dig response:

;; ->>HEADER<<- opcode: QUERY, status: REFUSED, id: 22254 ;; flags: qr rd; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0

Any idea as to why the status would be refused? All four domains are configured identically in DO’s DNS control panel.

Many thanks, Roop