If you turn on the AC and open the bonnet (aka 'hood' in USA), you should be able to see and hear the compressor clutch engaging/disengaging as the aircon cycles.

If you cannot see or hear the clutch engaging and disengaging, then that is a place to start.

There are quite a number of reasons why it won't cycle, but best to identify if that is the actual problem first.

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Cheers,

Anthony