U01 appears and the cooker will not enter pressure mode, often after a previous boil‑over.

Safety first: Ensure the cooker is not under pressure before touching the steam release valve.

• Set valve to SEAL: Rotate or flip the steam release handle to the SEAL or PRESSURE position as indicated on the Brock lid.
• Reseat valve cap: Remove the valve cap, clean it, and reinstall it firmly so it sits straight and fully down.
• Clean valve seat: Check the metal post or seat where the valve sits for dried food or starch. Clean with warm water and a soft brush, then dry.
• Inspect valve gasket: Look for cracks or hardening of the small silicone gasket under the valve cap. Replace if damaged.
• Test with water: Add water, lock the lid, set the valve to SEAL, and start a short pressure program. If U01 persists, the valve position sensor (if equipped) may be faulty and require service.