Arduino fail to powered by the micro usb and VIN pin

My Arduino nano BLE 33 sense worked normally by using the micro USB cable until I try to power it via the VIN pin today!!!
I connected my Arduino nano to a 3.3V DC secondary electrical power source (convert 12V to 3.3V ) via GND pin and VIN pin but failed to lite the POWER LED on. I thought maybe the voltage of the power source is not height enough cause the range of VIN should be 5~21V. I raise the voltage of my power source to 8V but the onboard POWER LED still went out.
I thought maybe sth went run so I connected my Arduino to my computer via a micro USB cable ( I wonder if I forgot to disconnect the GND pin and VIN pin to the 3.3V power ).

Later went I used the micro USB cable to power my Arduino I found it failed to be powered on( POWER LED is closed ). I check the GND pin and VIN pin while the Arduino is powered by the micro USB cable using the multimeter. The voltage between VIN and GND is 5V (maybe the board is already powered ) but the board didn't work. Then I tried hundreds of times to stick in and pull out the plug of the micro USB cable. I successfully turn on my Arduino board(the POWER led lighting) several times if I adjust an angle between the USB cable plug and my board to a certain position ( not work every time ). If I successfully turn on my Arduino board it can work normally till I pull out the cable plug. The problem remains when I try to reconnect the board to my computer.

I wonder if the board awaken system is crushed or sth else goes run? I want to know how to deal with the problem.

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