Secure the lid, move the valve to the sealing position, and hit Manual or Pressure Cook on High Pressure for 30 minutes for 5–6 lbs/1.5–2 racks of ribs (25 minutes for 2–4 lbs/1 rack). If you want the ribs slightly firmer, go for only 23 minutes for 5–6 lbs/1.5–2 racks of ribs (18 minutes for 2–4 lbs/1 rack). However, I do recommend you go for the longer cooking time in order to achieve that super-tender, fall-off-the-bone bite. (NOTE: The pot may take about 20 minutes to come to pressure due to the amount of liquid inside. You aren’t doing anything wrong!)