Got the car in for its MOT today. failed on Natural Idle Test

Engine speed - 879rpm

CO- 7.26% which is very high.

It failed 1st time on the Fast Idle Test but on the 2nd test, it passed on the FIT

what is wrong then? lambda sensor?

How to check for lambda values on vagcom. When I go the block 032, it shows N/A on all the 4 sections.

Any help appreciated. Thanks