Why can't the pdf file (wicked_pdf) open?

Question

Ruby on Rails

Shows:
"Error
Failed to load PDF document."
In controller:

respond_to do |format|
  format.html
  format.pdf do
    render :pdf => @event.tip_event.to_s + "_" + @event.id.to_s + ".pdf",
          :template => "events/_event_report.html.erb"
   end
end

Button:

<%= link_to 'Создать PDF документ', event_path(@event, :format => :pdf) %>

Where is the mistake?