In 99% of cases, most customers first become aware that there is an issue with their air-con when it isn’t blowing as cold as it used to, which is the sign that your car needs an air-con regas.
However, if the air-con has stopped working altogether and the air isn’t at all cooler, this indicates that more than just a regas is needed as the vehicle likely has a leak in the air conditioning system. This leak will need fixing before the system can be regassed.