A California response is generally due thirty days after service, and a default judgment is far harder to undo than to avoid.
People put the papers in a drawer. It is understandable and it is the single most expensive thing you can do, because a default judgment can be entered without further notice and then enforced against wages and accounts while you argue about setting it aside.
If you have been served, call an office rather than filling in a contact form. Say the words “I have been served” and give the date on the proof of service — any competent firm will put you through to a lawyer the same day.