Mercedes Repair Questions? Ask a Mechanic for Answers ASAP
Hi - if all of the connectors have been checked then I would suspect that one of the sensors is faulty - this is quite a common failure & the lights going straight into the red on the display is an indication that a fault code is stored.
To pinpoint the problem you will need a diagnostic tool such as Mercedes STAR - a test of the parktronic system will tell you what faults are in the system & if a sensor is faulty it will pinpoint which sensor is at fault
due to the age of the vehicle if no damage has been caused during the bumper swap procedure then this should be covered under warranty
Best regards, Paul