RESOLUTION
After Plesk Expand is upgraded to Plesk Expand 2.0, you need to upgrade DNS Controller software manually on each of your Central DNS servers. After upgrade is complete, log into Central DNS server via SSH service, and open /usr/local/dnscontroller/conf/hosts.allow file. Add a single
line with your Plesk Expand host name. See sample content:
# cat /usr/local/dnscontroller/conf/hosts.allow
my-expand-host.com Keywords: reload DNS