Update qbo_controller.rb

app/controllers/qbo_controller.rb

@@ -32,7 +32,7 @@ class QboController < ApplicationController
   # Called when the user requests that Redmine to connect to QBO
   #
   def authenticate
-    callback = request.base_url + qbo_oauth_callback_path
+    callback = qbo_oauth_callback_url
     token = Qbo.get_oauth_consumer.get_request_token(:oauth_callback => callback)
     session[:qb_request_token] = token
     # If Rails >= 4.1 you need to do this =>