This thread contains tips that help Fix "Sensing, Step Off, Thinking, Err" error message while trying to use Fitbit Aria to weigh yourself. Learn more?
If your scale displays "SENSING, THINKING, ERR," try removing the batteries for 10 seconds and then reinserting them. Restart the scale when ready. After that, make sure that you step on the scale barefooted and the scale is placed on a hard surface. If your scale displays "SENSING…STEP ON…STEP OFF" in a loop without displaying a measurement, remove the batteries for 10 seconds and then reinsert them. Be sure the scale is placed on an even surface and weigh yourself again.
If you continue to receive errors, contact Customer Support@ contact.fitbit.com/ for a replacement.