VCDS STFT and LTFT not updating

[sambb]

Hi,

Have a strange O2 sensor issue. Block 030's 3 digit number is showing that the sensor is heating, and ready but the last digit never 1's to show that it is active. In blocks 001, 032 and 033 the lambda % will never change and stays on 0%. If I introduce a lean condition (cam cover cap or dipstick) the STFT's and LTFT's do not move and remain on 0%. All this made me think that the sensor is a dud yet the yet in block 031 the lambda sensor specified and active values update continuously.
I swapped out the o2 sensor for a working spare from my old car and it is exactly the same.
So I'm thinking the lambda % stuck on 0% in their various places and the fact that the fuel trims don't respond is evidence that there is no closed loop happening. Open loop seems to be working though ie when looking at block 031 in a 3rd gear pull will see actual lambda throughout the run and you can drive around and watch it real time.
Oh and the car was well and truly hot and up to temp. Drove around for hours and the STFT's don't oscillate and LTFT's are bolted to zero. There is just nothing going into them and the sensor never goes active. Fault in the ECU? a fuse??

So whats the cause of that??? please help. I have an event on Sunday and need to get this sorted. I have VCDS and unisettings that I can use as diagnostics etc so any advice welcome
thanks
sam