Help needed Parking Aid Button Flashing and No Parking Sensors Working

[fordlynx]

Fiesta 2010 Titanium factory fitted sensors front and rear 

The front parking aid button under climate control flashes when button pressed or reverse engaged and also get 1 long beep followed by a short beep then nothing just flashing led on button.

Any help or ideas in right direction most appreciated

[leon freeman]

i have the same or very similar fault if the ignition is on but engine not running they work fine when the engine is started i have long beep and led flashing on the parking sensor button and nothing ford s max 58 1.8 diesel