I purchased this product three days ago and it started off working fine (once I had deleted and reinstalled the app three times in order to get it to link), but now neither the stress level nor the body battery record a reading. I have tried plugging it in to the charging cable to see if it reboots and have synced it with the app a dozen times, but still nothing. When I try to get readings from either of them, the device just times out and the screen goes black. Is there a way of rectifying this?