Server: OpenVPN Access Server 2.0.24
Clients: OpenVPN Connect 2.0.18.202 (Windows)
From some locations we are having following error and we are not able to connect:

Some of these locations are from airports or hotels (sometimes in Middle East).
Does the "DNS lookup failed" message means that the DNS server isn't able to translate the URL to the IP address?
In that case what is the workaround?
Is there anything I should check?