It was probably running R-22 which you can still get but it isn’t manufactured anymore. It’s ozone depleting so all production and import of the stuff was completely banned in 2020 and it has been in the process of being slowly phased out since 2004. The only source for it is stuff recovered out of other systems or any existing stocks which are running out very quickly. That means it gets more expensive every year. Now a days most HVAC companies will just replace those systems rather than fixing them for that reason.