My cruise stopped working when the brake light switch went. It did throw a fault code to dash and you could see it in VAGCOM. There are 2 brake switches I believe but only one is cruise control related. My rear brake lights did not work I think so check them. It is unlikely to be a chip issue as the cruise is controlled by the "central convenience controller" and the engine ECU only gets one wire added which maybe just "turns on" the "hold that rpm" function for the ECU.. my notes say;
"Engine fault, flashing heating coil, service symbol and no Cruise control
1 Fault Found = 16955 - Brake Switch (F)
P0571 - 35-00 - Implausible Signal
Measure block 006 .. second box labelled Brake Switch 000= pedal up 011 = pedal down
… the broken one only did 001
Removed a 380-945-511 switch which is brown and replaced with 6Q0-954-511 which is black
You have to rotate switch about 30 degrees until it clicks before it will become active."
The dealer can check for brake and clutch switches.. and cruise button. Maybe something silly like the brake switch as it was fiddly to turn the 30 degrees to get it to click and become active.
Mine is a 2005
Cupra .. so no factory CC so I DIY'ed it.