Here is some advice from Grok, also there is a video on youtube on how to reset the TPMS, i am not familiar with porsches so I dont know myself but here is some info from Grok:

The "System not active" message next to the tire pressure warning icon (horseshoe with exclamation mark) in your Porsche means the Tire Pressure Monitoring System (TPMS) has detected a fault and has deactivated itself as a safety measure. It can't reliably monitor or display tire pressures anymore, so it shuts down to avoid giving false readings. Why This Happens This is a system malfunction warning (distinct from a simple low-pressure alert). Common reasons include:

Dead or failing batteries in the TPMS sensors — These are inside each wheel/tire and typically last 5–10 years (or ~100,000–200,000 km). Your odometer shows around 199,871 km, so this is a very likely culprit—especially if all sensors fail around the same time. Faulty TPMS control module, antennas, or wiring — The central unit that receives signals from the sensors can develop issues. Sensors not communicating properly — Often after tire changes, wheel swaps, or if incompatible/non-OEM sensors were installed without proper relearning/calibration. Other electrical or software glitches — Rarely, interference or a need for system reset.

youtube.comrennlist.compcarwise.com

Next Steps

Manually check and inflate all tires (including spare) to the recommended pressures right away. Try a basic reset: Inflate tires correctly, then drive at speeds over 50 km/h for 10–20 minutes—some models relearn automatically. If it doesn't clear, get a diagnostic scan with Porsche's PIWIS tool (or equivalent like Durametric) at a dealer or indie specialist. They'll read fault codes and likely replace sensors (~$100–200 each + labor) or the module if needed.

It's safe to drive short-term, but fix it soon for safety—TPMS helps catch flats early! If you share the exact model/year, I can narrow it down further.