Turning off parking sensors - possible fault

When I hooked up my caravan to move it yesterday the parking sensors refused to turn off. Usually I just touch the button on the screen to turn them off, has anyone else had similar problems?
I did have a problem with the alarm not switching off a couple of months ago and the dealer put in a new electronics box to deal with that.

I can't think of anything I have done that would stop it from switching off.

Thanks