Tried again just now (17 hours after first post). Again, couldn't retrieve the key. The connectivity test passed again. However, I could not ping noc1 from the blog's host system.
%ping -c 4 noc1.wordfence.com
PING noc1.wordfence.com (69.46.36.8): 56 data bytes
--- noc1.wordfence.com ping statistics ---
4 packets transmitted, 0 packets received, 100.0% packet loss
However, I can connect to noc1 on port 80:
%telnet noc1.wordfence.com 80
Trying 69.46.36.8...
Connected to noc1.wordfence.com (69.46.36.8).
Escape character is '^]'.
Any ideas what the problem may be?