OP do not pay out to have the radar recalibrated this is not the issue. Calibration is loaded at the radars manufacture.
The issue is probably the radar is out of alignment/loose
You will need VCDS. There should be faults stored under the radar. Too many faults and the radar wont run...
Reset faults and then see what comes back.
Using the measuring blocks you should be able to see the angle that radar is at and the deviation value, if its not set up corectly.
Google front radar retrofit and some topics cover corect placement
Dealers are pretty clueless and dont have the kit to calibrate either the front assist or adaptive cruise control.