What causes the air conditioning to blow warm air in an Audi A2?

I have an Audi A2 and recently the air conditioning has been blowing warm air instead of cold. It used to work perfectly fine. What could be the cause of this issue?

One possible cause could be a refrigerant leak. The air conditioning system may be low on refrigerant, which can cause the air to blow warm.

Another potential cause could be a faulty compressor. If the compressor is not functioning properly, it can prevent the air conditioning system from producing cold air.