Are these two Arduino Pro Micros jumpered correctly?
At a glance, the operating frequency of the XTAL on board may tell the operating voltage of your Arduino.

If the XTAL is 16MHz, the device is probably 5V.
If the XTAL is 8MHz, the device is probably 3.3V.

Make sure to use a multimeter and trace the power pins to the jumper / LDO. Also measure voltage at LDO output to see if LDO is active or not.