undefined method `has_attachment' #145

After setting all the items according to the documentation, I'm getting this error when I try to run the server

/gems/ruby-2.3.3@r426/gems/activerecord-4.2.6/lib/active_record/dynamic_matchers.rb:26:in method_missing': undefined methodhas_attachment' for User (call 'User.connection' to establish a connection):Class (NoMethodError)
Iḿ generate all files and included the require "attachinary/orm/active_record" in the applicationController.

Also included the rout: mount Attachinary::Engine => "/attachinary" and run the migrations.

Has anyone ever come across this problem? Thanks!