I have CC2650STK bought in last June and two others of same the model. They were working fine before 2019. It happened a few time that when I turn the sensor on red LED blinks and then green. After some such iterations [red then green] now, when I turn them on no LED blinks, it seems as if they are dead. This is happening to all three of them at the same time although I have changed their battery as well but no luck. I don't have devpack to see what could be potential problem. Can you please guide me on this?