That tells me you haven't set up the 'demo' subdomain at your dns provider. The output of 'dig' also suggests that to be the case.
paul@G620:~$ host meritsystemservices.com
meritsystemservices.com has address 18.104.22.168
paul@G620:~$ host demo.meritsystemservices.com
Host demo.meritsystemservices.com not found: 3(NXDOMAIN)
The same for 'ping'.
paul@G620:~$ ping -c 1 meritsystemservices.com
PING meritsystemservices.com (22.214.171.124) 56(84) bytes of data.
64 bytes from ec2-54-245-65-104.us-west-2.compute.amazonaws.com (126.96.36.199): icmp_req=1 ttl=43 time=164 ms
--- meritsystemservices.com ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 164.497/164.497/164.497/0.000 ms
paul@G620:~$ ping -c 1 demo.meritsystemservices.com
ping: unknown host demo.meritsystemservices.com