Michael

For those who are using Rails 7:

Rails 7 has Hotwire enabled by default, and it will validate the response status code. For failed validation, the status code should be 422 (Unprocesssable entity). Otherwise, Hotwire may believe the form is valid, hence it doesn't work.

So in you registrations_controller create method, instead of

else
render :new
end

add a status option

else
render :new, status: :unprocessable_entity
end

This way Hotwire knows "Hey, the form is invalid", and the validation shall work.