I have just deployed EPiServer Find to one of my EPiServer Azure Websites with automatic deploy from github and it crasched saying "Could not load file or assembly 'System.Web.Http 4.0.0 ...." that EPiServer Find UI is using.
I got it to work by upgrade my site to MVC5 because it added version 5.2.0 of this assembly but you might have to look into the dependencys for the nuget package
This looks like the same issue I blogged about a little while ago - http://www.markeverard.com/2014/06/26/finding-missing-dependencies-when-installing-new-episerver-find/
Shame its not been fixed yet :(
There is also a problem with the updates from EPiServer when it is not supporting the same version of WebAPI Webhost, the nuget package you need to install. I had to grab an older version just because episerver find did not support the latest newtonsoft json nuget package. Getting to know the nuget package manager console is worth looking into.