I am facing the same problem.
My project - Sitefinity 8.0.5700, Feathers 1.2.260.1. The textbox rendered doesn't show any autocomplete. The Search button doesn't respond at all. No redirect or error in both console and logs. Upgrading to Feathers 1.2.290.1 doesn't work either.
Then, I tried creating a new project with Sitefinity 8.0.5710, default Feathers version. The search widget is able to work properly (autocomplete, redirect, etc)
I have no idea what went wrong with my project. Is the widget depending on some dll which i might be missing in the projects?
Thanks in advance.