Debuging Devise in simple Rails app - ruby-on-rails

Question

I configure Devise gem for Rails and in code it seems look OK but when I'm trying to register new user I have the problem.
In register form Devise show notice:
Please review the problems below:
but that's all. Nothing specific message. Where I should looking for first? How to debug something like this?
Any suggestions?
Log from rails server:
Started POST "/auth/register" for 127.0.0.1 at 2014-09-14 17:09:13
+0200 Processing by Devise::RegistrationsController#create as HTML Parameters: {"utf8"=>"✓",
"authenticity_token"=>"iRsLU68tBckSzK1tupMoXZQlGw7xOuzMlfuiIVVs+rc=",
"user"=>{"email"=>"test#test.com", "password"=>"[FILTERED]",
"password_confirmation"=>"[FILTERED]"}, "commit"=>"Sign up"}
(0.2ms) BEGIN User Exists (0.4ms) SELECT 1 AS one FROM "users"
WHERE "users"."email" = 'test#test.com' LIMIT 1 (0.2ms) ROLLBACK
Rendered devise/shared/_links.haml (0.5ms) Rendered
devise/registrations/new.html.haml within layouts/application (15.9ms)
Completed 200 OK in 121ms (Views: 24.2ms | ActiveRecord: 0.8ms)
And when I try log in:
Started POST "/auth/login" for 127.0.0.1 at 2014-09-14 17:10:23 +0200
Processing by Devise::SessionsController#create as HTML Parameters:
{"utf8"=>"✓",
"authenticity_token"=>"iRsLU68tBckSzK1tupMoXZQlGw7xOuzMlfuiIVVs+rc=",
"user"=>{"email"=>"test#test.com", "password"=>"[FILTERED]",
"remember_me"=>"0"}, "commit"=>"Sign in"} User Load (0.7ms) SELECT
"users".* FROM "users" WHERE "users"."email" = 'test#test.com' ORDER
BY "users"."id" ASC LIMIT 1 Completed 401 Unauthorized in 2ms
Processing by Devise::SessionsController#new as HTML Parameters:
{"utf8"=>"✓",
"authenticity_token"=>"iRsLU68tBckSzK1tupMoXZQlGw7xOuzMlfuiIVVs+rc=",
"user"=>{"email"=>"test#test.com", "password"=>"[FILTERED]",
"remember_me"=>"0"}, "commit"=>"Sign in"} Rendered
devise/shared/_links.haml (0.4ms) Rendered
devise/sessions/new.html.haml within layouts/application (9.8ms)
Completed 200 OK in 106ms (Views: 15.4ms | ActiveRecord: 0.0ms)

Answer 1

I debug these things by inspecting the object.errors
In this case, try to
raise #user.errors.inspect
Somewhere after the save in the create method