You file an order to show cause and write that you never received papers.
Write your defenses to the landlord’s case.
If you do not know why the landlord brought you to court, you can go to the clerk’s office and ask to see your court file.
The petition should be in the court file. It will state why the landlord is bringing you to court. It should include an affidavit of service notarized by a process server.