I see. So one would connect the voltage divider to the 3V3 output pin in the Particle to avoid an issue of over-voltage, as described by the OP.
great tip, thank you.
@rhafner6 : check if you can connect the probe to 3V3, instead of 5V, in order to protect your Particle from over-voltage.
EDIT: This may fix your issue, so try it out and let us know please