I got the latest firmware 3.1.9 and having read release notes about improvements to measurements, I looked at my numbers and I am wondering if they are correct.
Did you have much higher numbers before the firmware update?
I often see 0 in my home with a good HVAC filter. Your PM 0.3 count is still registering, so data is coming in from your sensor, but low values
The numbers were higher some days earlier, but it was before the new firmware was released I believe.
You would need to compare the numbers with outdoors. Air quality can fluctuate quite a lot.