Looks like the tech has checked the Low side port pressure of the AC.
Without the compressor running the pressure throughout the AC system equalizes and will be around 10 bar on any port (depending on temperature, volume in the system etc.).
With the compressor running the compressor suction side pressure (Low side) should indeed drop as it compresses the gas raising it on the discharge side (High side). Around 2 bar on the Low side is about right with the system running.
If it's not doing anything when AC is requested then it's likely an electrical problem where the compressor is not engaging.
Why it's not engaging could be for a number of different reasons. It could be a faulty sensor, wiring issue, faulty HVAC ECU module or failed compressor clutch engagement coil amongst other problems.
I would hope these were all checked before the Tech condemned the compressor itself.
A diagnostic tool can be used to command the compressor on ignoring all other sensors and inputs. If it doesn't work when commanded by the tool then the clutch coil circuit needs checking. If it does work then the HVAC system sensors and wiring needs checking.
Without a diagnostic tool then the coil resistance can be checked (should be no more than a few Ohm) and 12V supplied to it to see if it can operate the clutch on the front of the pulley.
Unfortunately you are reliant on the garage to be able to investigate electrical faults to definitely confirm where the problem lies. That takes knowledge and time which it seems nowadays very few garages are able and willing to do. They tend to go down the route of replacing parts until they get lucky. Given hourly rates that are charged for diagnostics of a fault then the part changing route might actually work out cheaper to the customer but it's a gamble that might mean perfectly good parts are replaced for no reason.
Of course they might well have done those checks and the compressor is broken, the 10 bar and 2 bar answer you got though is not a definitive answer to condemn the compressor.
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