My 2017 glc300 shows "collision prevention assist plus inoperative" every time engine starts for 2 years.
I thought it's hardware issue but
recently I found youtube video explaining it's software issue and can be fixed by MB Xentry $$$$$ , or Autel expensive model obd $3k.

This is one of many videos,
https://youtu.be/lZktp9NPtyA
(video shows a little different reset menu than my below menu. Seems like because Xentry version difference.)

I chose to install Xentry into my old laptop, i ordered openport2 obd device for $25 at AliE, and downloaded Xentry software and fix files thru many sources,
and after hundreds hours struggle, finally Xentry working. (There are AliE sellers offer remote Xentry installation for $50)

My Xentry found
B220600 code;
The current vehicle identification number is incorrect or not present.

(This error can not be found by regular obd tool. My cheaper Autel obd $150 with mb module didn't find it)

if you have Xentry tool, or if you go and ask MB dealer, this code can be cleared by doing this,

1. Go to
A90 - Control unit 'COLLISION PREVENTION ASSIST' (SG-AWF)S menu

2. Click Menu "author data"

3. click on "autoliv_config"
(yes, just click. No response is normal)

4. Engine start.
No more inoperative message.