DIAGNOSIS Yeah, this one's common. 'PF' stands for Power Failure. It's not about your house's power, it's the unit's internal memory getting scrambled from a brief outage or surge.
FIX You need to do a hard reset. First, unplug the dehumidifier from the wall. Don't just turn it off at the unit, physically pull the plug. Wait a full 60 seconds—seriously, time it. Then, plug it directly back into the wall outlet (not a power strip). It should boot up normally and the PF code should be gone.
IF THAT DIDN'T WORK If PF comes right back after the reset, the control board might have taken a hit. Try plugging it into a different, known-good outlet in another room. If it still flashes PF there, the main PCB is likely fried and needs replacement.
HEADS UP These things are sensitive to dirty or unstable power. Plugging it into a cheap power strip or an outlet on a circuit with other big appliances (like a fridge kicking on) can sometimes trigger this. A good surge protector is a cheap insurance policy.