Simple form in rails doesn't display validation error messages - ruby-on-rails

Question

I have this simple_form in my app but it doesn't display any validation error messages:
<%= simple_form_for(#user) do |f| %>
<%= f.error_notification %>
<%= f.input :first_name, label: "Prénom" %>
<%= f.input :last_name, label: "Nom" %>
<%= f.input :email, label:"email" %>
<%= f.input :telephone, label: "telephone"%>
<p><%= f.label :birthdate, 'Date de naissance' %></p>
<%= f.date_select :birthdate, {:include_blank => true, :default => nil, :use_month_names => ['Janv.','Fevr.', 'Mars', 'Avr.', 'Mai', 'Juin', 'Juil.', 'Août','Sept.', 'Oct.', 'Nov.', 'Déc.'], :order => [:day, :month, :year], :start_year => 1910, :end_year => 1995} %>
<%= f.input :genre, label: "Sexe" %>
<%= f.input :ranking, label:"Classement" %>
<%= f.input :licence_number, label: "numéro de licence"%>
<p>
<%= f.label :Photo%>
<%= f.file_field :picture %>
</p>
<p>
<%= f.label :licence %>
<%= f.file_field :licencepicture %>
</p>
<p>
<%= f.label :certificat %>
<%= f.file_field :certifmedpicture %>
</p>
<div id="validation"><%= f.submit %></div>
<% end %>
Here are my validations in my user model
validates :first_name, presence: { strict: true }, on: :update
validates :last_name, presence: { strict: true }, on: :update
and you can have a look at my simple_form.en.yml:
en:
simple_form:
"yes": 'Yes'
"no": 'No'
required:
text: 'required'
mark: '*'
# You can uncomment the line below if you need to overwrite the whole required html.
# When using html, text and mark won't be used.
# html: '<abbr title="required">*</abbr>'
error_notification:
default_message: "Certains champs posent problèmes:"
My update method:
def update
#user.update(user_params)
#user.create_mangopay_natural_user_and_wallet
redirect_to user_path(current_user)
end
I don't get why the error notifications don't display as I have the proper f.error_notification in my view

Answer 1

As revealed in your comments, your controller doesn't check for a successful save and just blindly redirects to the user page. I didn't see any native functionality from simple_form that does this for you. You need to check for this successful save and re-render the edit form on failure so it can show those errors in f.error_notification:
def update
if #user.update(user_params)
#user.create_mangopay_natural_user_and_wallet
redirect_to user_path(current_user)
else
render 'edit'
end
end