Parking sensor - no sound

[fsut]

Hi guys,

We fitted a whole OEM (but used) parking package to my car.
It used to work as if I put the car in reverse the button lights on and it bleeps once. But I can't get any other sound.
- I'm also able to turn it on/off

I was told that the speaker seems to be broken so I need to get an other one but the ''new one'' is also in complete silence.

Is it possible that the speaker's (roof) cable is broken?
Or I was so lucky that I purchased an other broken speaker?
- is there an alternative speaker that could be fitted?

How can I make sure what's going on?
Do you have any idea?

[fsut]

Here is the solution:
2 wires were missing from this harness:
https://i.imgur.com/zPnGYhq.png

Solution:
https://i.imgur.com/0RS8qkp.png

I hope that sometime this will help someone