ruby on rails - How to prevent automatic rollback when trying to set user as admin -

hi active admin installed on app; trying set new user admin using rails console. selecting specific user in table user. writting

user.admin = true  

then

user.save 

but

  (0.2ms)  begin    (0.3ms)  rollback => false 

i have automatic rollback... doing wrong ? here's user model

class user < activerecord::base   after_create :send_welcome_email     # include default devise modules. others available are:   # :confirmable, :lockable, :timeoutable , :omniauthable   include algoliasearch   algoliasearch index_name: "user#{env['algolia_suffix']}"     attribute :email, :licence_number, :ranking, :first_name, :last_name     attributestoindex ['email', 'licence_number', 'ranking','first_name', 'last_name']   end    extend enumerize     enumerize :genre, in: [:male, :female]     enumerize :ranking, in: ['nc', '30/5', '30/4', '30/3', '30/2', '30/1', '30', '15/5', '15/4', '15/3', '15/2', '15/1', '15', '5/6', '4/6', '3/6', '2/6', '1/6', '0', '-2/6', '-4/6', '-15', '-30']    23    devise :invitable, :database_authenticatable, :registerable,          :recoverable, :rememberable, :trackable, :validatable,          :omniauthable, :omniauth_providers => [ :facebook ]   has_many :subscriptions, dependent: :destroy   has_many :tournaments, dependent: :destroy   has_attached_file :picture,     styles: { medium: "300x300>", thumb: "100x100>" }    validates_attachment_content_type :picture,     content_type: /\aimage\/.*\z/    has_attached_file :licencepicture,     styles: { medium: "300x300>", thumb: "100x100>" }    validates_attachment_content_type :licencepicture,     content_type: /\aimage\/.*\z/    has_attached_file :certifmedpicture,     styles: { medium: "300x300>", thumb: "100x100>" }    validates_attachment_content_type :certifmedpicture,     content_type: /\aimage\/.*\z/   validates :first_name, presence: { message: 'veuillez remplir votre prénom' }, on: :update  validates :last_name, presence: { message: 'veuillez remplir votre nom' }, on: :update   validates :iban, format: {         with: /\a[a-za-z]{2}\d{2}\s*(\w{4}\s*){2,7}\w{1,4}\s*\z/,         message: 'le format de votre iban doit être du type fr70 3000 2005 5000 0015 7845 z02'     }, on: :update   validates :bic, format: {         with: /([a-za-z]{4}[a-za-z]{2}[a-za-z0-9]{2}([a-za-z0-9]{3})?)/,         message: 'le format de votre bic doit être du type axabfrpp  '     }, :allow_blank => true, on: :update    validates :telephone, format:{         with: /\a(\+33)[1-9]([-. ]?[0-9]{2}){4}\z/,         message: 'le format de votre numéro doit être du type +33602385414'     }, :allow_blank => true, on: :update    has_many :messages   has_many :notifications    def self.find_for_facebook_oauth(auth)     where(provider: auth.provider, uid: auth.uid).first_or_create |user|      user.provider = auth.provider      user.uid = auth.uid      user.email = auth.info.email      user.password = devise.friendly_token[0,20]      user.first_name = auth.info.first_name      user.last_name = auth.info.last_name      user.picture = auth.info.image      user.token = auth.credentials.token      user.token_expiry = time.at(auth.credentials.expires_at)    end  end    # def initialize   #   @errors = activemodel::errors.new(self)   # end     def age     = time.now.utc.to_date     now.year - birthdate.year - (birthdate.to_date.change(:year => now.year) > ? 1 : 0)   end   def full_name     if last_name != nil && first_name.nil?       "#{last_name.capitalize}"     elsif first_name != nil && last_name.nil?       "#{first_name.capitalize}"     elsif last_name.nil? && first_name.nil?       ""     else       "#{first_name.capitalize} #{last_name.capitalize}"     end   end    def create_mangopay_natural_user_and_wallet     natural_user = mangopay::naturaluser.create(self.mangopay_user_attributes)       wallet = mangopay::wallet.create({       owners: [natural_user["id"]],       description: "my first wallet",       currency: "eur",       })      kyc_document = mangopay::kycdocument.create(natural_user["id"],{type: "identity_proof", tag: "driving licence"})      self.mangopay_natural_user_id= natural_user["id"]     self.wallet_id = wallet["id"]     self.kyc_document_id = kyc_document["id"]     self.save   end     def mangopay_user_attributes     {       'email' => self.email,       'firstname' => self.first_name,       'lastname' => self.last_name,  # todo: change this! add 2 columns on users table.       'birthday' => self.date_of_birth.to_i,  # todo: change this! add 1 column on users table       'nationality' => 'fr',  # todo: change this!       'countryofresidence' => 'fr' # todo: change this!     }   end    private     def send_welcome_email     usermailer.welcome(self).deliver   end end 

since validation issue, take @ the guide. errors:

user.errors.full_messages