You probably need to increase the sleep frequency above the level at which the pump can move water and build pressure. If you are not increasing the pressure and creating flow at 46 Hz, and your sleep frequency (P08.10) is 42 Hz, then the drive will sit there happily running and holding pressure until the water boils in the pump housing.

I have set up many VFDs for pressure control PID with other models of drive and usually the wake setting is related to the feedback signal units (psi or gpm, for example). With the GS20, the wake signal appears to be based on the calculated command frequency, so I am not sure what to recommend there except some trials. You may need to raise it to a higher level than the sleep frequency at least long enough to prove that the sleep frequency value actually does trigger sleep mode and isn't being overruled by the wake value.