What it usually means
A booster pump that keeps running is often trying to reach a pressure it cannot achieve or is being told by the controls that pressure is still too low.
Possible causes
Possible causes include a leak on the system, failed non-return valve, loss of pressure vessel charge, faulty pressure transducer, incorrect set point, worn pump, blocked inlet or high demand from the building.
Safe checks
Look for obvious leaks, check whether taps/outlets are open, note the pressure gauge reading, take a photo of the control panel and confirm whether one pump or multiple pumps are running.
Why it should not be ignored
Continuous running can increase wear, overheating risk, energy usage and the chance of a full booster pump failure.