I have problems trying to configure OpenDNS. I have contacted OpenDNS support but they did not answer. I cannot access websites like Twitter and Facebook.

I tried welcome.opendns.com (did not work, shows not using OpenDNS.

Using nslookup:
$ nslookup -type=txt which.opendns.com. 208.67.222.222
Server: 208.67.222.222
Address: 208.67.222.222#53
Non-authoritative answer:
which.opendns.com text = "7.sin"
Authoritative answers can be found from:
$ nslookup -type=txt debug.opendns.com.
Server: 127.0.1.1
Address: 127.0.1.1#53
Non-authoritative answer:
debug.opendns.com text = "server 3.sin"
debug.opendns.com text = "flags 20 0 2f6 0"
debug.opendns.com text = "id 13521181"
debug.opendns.com text = "source 222.164.129.44:62574"
Authoritative answers can be found from:
$ nslookup www.exampleadultsite.com.
Server: 127.0.1.1
Address: 127.0.1.1#53
Non-authoritative answer:
Name: www.exampleadultsite.com
Address: 67.215.92.210