Custom form for active admin is not displaying

I have added a piece of code in my active admin model for input form, but weirdly, it's not getting displayed, instead, it's showing the default form. Neither it's showing any error nor displaying my custom form.

form do |f|
f.inputs do
  f.input :email
  f.input :phone
  f.input :gender
  f.input :birthday
  f.input :password
  f.input :password_confirmation
  f.input :us_citizen
  f.input :invitation_limit
end
f.actions

end