What to do if sensor returns a reading with "Hardware Failure".
For sensors powered by coin cell batteries, this reading is usually caused by improper battery placement. The battery will need to be pushed farther into the housing, as its placement is interfering with the sensors ability to measure data. The battery is likely touching the circular ports on the edge of the circuit board inside.
Use a tool like a toothpick, paper clip, or other slender object to push the battery out of the sensor through the battery removal hole.
Wait 60 seconds to make sure that the sensor's power capacitor has a chance to fully discharge.
Insert the battery back into the sensor as far as it will go, using the tool (toothpick, paperclip etc.) that you used to remove the battery. (Thumbs may not do the trick.)
Check the software to make sure that the sensor is displaying the proper information. If not, repeat this process. If the sensor continues to show this error message, the sensor may be broken. Contact Monnit customer support to arrange a replacement if the sensor is still under warranty.
If the sensor is powered by AA batteries the sensor may be broken. Remove the batteries, wait 60 seconds, then reinsert the batteries to see if the reading changes. If it does not, contact Monnit customer support to arrange a replacement if the sensor is still under warranty.