html - Bootstrap form formatting not applying -

i trying add form subscription emails instance variable @premail in embedded ruby

for reason form not have bootstrap styling when load on localhost. i've tried several things can't form bootstrap input form. here code form:

    <div class="container-form">             <%= form_for @premail, html: {class: "form-horizontal home-form", role: "form"} |f| %>               <% if @premail.errors.any? %>                                    <h2><%= pluralize(@premail.errors.count, "error") %> prohibited link being saved:</h2>                   <ul>                   <% @premail.errors.full_messages.each |msg| %>                     <li><%= msg %></li>                   <% end %>                   </ul>               <% end %>               <div class="form-group">                 <p> stay updated our launch! </p>                 <%= f.label :email, class:"col-sm-2 control-label" %>                 <%= f.email_field :email, autofocus: true, class:"form-control", placeholder:"enter email" %>               </div>               <div>                 <%= f.submit "sign up", class:"btn btn-default" %>               </div>             <% end %>       </div> 

what missing?