Smartthings Water Sensor won't turn on at all

I have a Smartthings Water Sensor that stopped responding (showed battery level in the 50%+ range). I went ahead and replaced the battery anways to see if that would help, but nope. I can’t even get it to reset so I can try to re-pair it. Holding down the reset button does nothing. The LED never even turns on. Not sure what to do at this point… Any ideas?

When did you buy the sensor?