Chromecast worked immediately when connected.
However I connected it to the house internal network that is running on my own wireless-n Gbit router (dlink dir-655) rather than the ancient Verizon Westell 100Mbit wireless-g network.
Casts fine via Android phone and from PCs. One thing I did discover is that the Chrome extension on a PC running SEP av (Symantec End Point protection) cannot find the chromecast device. Uninstalling SEP and replacing it with Avast resolved that issue.