Did you restart your machine?
Update:
I ran into the same problem myself! It happened when I installed version 1.6 over 1.5. When I restarted my machine, I found Tortoise entries in Start Menu but not via context menu. When I clicked on “Settings” an error message appeared. So, I uninstalled 1.6 and installed it anew. Now it’s working again! Yes, available through context menu. I believe it’s a bug.