The pins labeled COM are all ground (GND). Connect ST (self test) to GND and apply 3.3V power to the Vs pins.
If you are using a module with the sensor mounted, post a link to it.
If you are using the naked chip, I hope you have very carefully soldered all the connections, with no solder bridges or bad joints. You need a decoupling capacitor (typically 0.1 uF) between Vs and COM/GND, as close as possible to the chip.