Following the datasheet specification strictly, > 3.6 V input voltage is only allowed if Vdd is in the 2.7V to 3.3 V range, so the operation conditions described in post #1 might have already damaged the chip. I have no experience with this specific chip and don't know if damage by slightly exceeding of maximum ratings is likely. I would rather expect that a more serious overvoltage event has destroyed the chip. Or could it be soldered incorrectly, causing shorts with other pins?