Version 3.20 of TopoFusion is experiencing trouble connecting to the Canadian Topo map server. We are have a fix and are testing it in the latest beta. We should have Version 3.22, with the fix, released within the next few days.
Thanks for the patience. Until then you will get a "cannot connect to server" message when trying to download Canadian maps.
All other tilesets and map servers are up and functioning great.