If I remember correctly, that is a DNS resolution issue. I am running the site on a web host. I have verified that cURL support is enabled as it should be. Please note that the web address is not set in public DNS; instead it is mapped to the host IP address in my hosts file. I have entries for both the naked base domain and the www-qualified version, e.g. "xyz.com" and "http://www.xyz.com", but I have tried it with just one at a time as well. It does not appear the hosts entry has anything to do with the problem.
I'm running Joomla 3.7.4 with PowerAdmin 2.5.1.