Devise: Forbidden Attributes Error on Sign Up - ruby-on-rails

Question

I have set up devise. I added database authentication, only in the first instance. I was able to fill out the form and add it to my db. I then added omniauth and now, when I try to register using the form, rather than the social media options, I get a forbidden attributes error.
My view is:
<% if user_signed_in? %>
<li>
<%= link_to('Edit registration', edit_user_registration_path) %>
</li>
<% else %>
<li>
<%= link_to 'Register', new_user_registration_path, :remote => true, 'data-toggle' => "modal", 'data-target' => "#myModal", :method => 'get' %>
</li>
<div class="modal fade" id="myModal" tabindex="-1" role="dialog" aria-labelledby="myModalLabel" aria-hidden="true">
<div class="modal-dialog">
<div class="modal-content">
<div class="modal-header">
<button type="button" class="close" data-dismiss="modal" aria-hidden="true">×</button>
<h4 class="modal-title" id="myModalLabel">Request an invite</h4>
</div>
<div class="modal-body">
<%- if devise_mapping.omniauthable? %>
<div class="facebookauth"> <%= link_to "Register with Facebook", user_omniauth_authorize_path(:facebook) %></div>
<br />
<% end -%>
<%- if devise_mapping.omniauthable? %>
<div class="linkedinauth"> <%= link_to "Register with LinkedIn", user_omniauth_authorize_path(:linkedin) %></div>
<br />
<% end -%>
</div>
<div class="modal-footer">
<%= simple_form_for(resource, as: resource_name, url: registration_path(resource_name)) do |f| %>
<%= f.error_notification %>
<div class="form-inputs" style="padding-left:15%; text-align:left;">
<%= f.input :first_name, required: true, autofocus: true %>
<%= f.input :last_name, required: true, autofocus: true %>
<%= f.input :email, required: true, autofocus: true %>
<%= f.input :password, required: true %>
<%= f.input :password_confirmation, required: true %>
</div>
<div class="form-actions" style="padding-left:15%; padding-top:5%; text-align:left;">
<%= f.button :submit, "Register" %><% end %>
</div>
</div>
</div>
</div>
</div>
<% end %>
My application controller has this:
def configure_permitted_parameters
devise_parameter_sanitizer.for(:sign_up) { |u| u.permit( :first_name, :last_name, :email, :password, :password_confirmation) }
devise_parameter_sanitizer.for(:sign_in) { |u| u.permit( :email, :password, :remember_me) }
end
I have just tried adding this to my user/registrations_controller, but it does not help.
def user_params
params.require(:user).permit(:first_name, :last_name, :email, :password, :password_confirmation )
end
I'm wondering if its because I don't have fields in my database for password or password confirmation? I have 'encrypted password'.
Any help would be very much appreciated.
Thank you