Togaking said over 3 years ago on Progressive Web Applications :
This was an excellent presentation - I directly migrated all functionality, excluding the installation of my manifest.json file directly from the presentation.

Following the video, and migrating to match, my manifest.json file won't download - it looks like it can't even be seen.  

In my applcation.html.haml file, I have 

%link{:href => "/manifest.json", :rel => "manifest"}/

after that, I update my routes.rb to contain manifest.json as a route

get '/service-worker.js', to: 'service_workers/workers#index'
get '/manifest.json', to: 'service_workers/manifests#index'

And finally, I have, per your code, a directory named service_workers inside of views, with manifests/index.json.erb and workers/index.js.erb inside of it.  Everything works perfectly, excluding the ability to see/download/install my PWA, because manifest.json isn't found.

Did I miss something?  Do I need to do something else to get the manifest.json file to be seen/downloaded?