Bladder type accumulators are not 100 % airtight ,so need air added every few months. Switch off the pump
open a tap [ faucet ] then check the air pressure. The air pressure should be less than the pumps cutoff water
pressure e.g. 18 PSI of air to 20 PSI of water pressure. If You don't have a guage add air until pump appears to cycle normally .
The bladder will eventually rupture if air runs out.