Well the official info for this P0520 on the 1.4 Multiair is:
334 - 500X 1.4 Turbo MultiAir Oil pressure switch (Signal incorrect
after event) P0520-00
Sadly there are no normal diagnostic charts for this error code. Title only and blank sheet!
If new sensor then probably a wiring problem. Check the sensor wires and nearby connector. You could also try popping and engine ECU connectors and using some switch clean/lubricate fluid. Disconnect the battery -ve first though.
