Opening Serial Plotter or Serial Monitor sets the board into dfu

[Grumpy_Mike]

@anirudh_anil

Then I accidentally shorted the GND pin and the Reset pin.

That is no problem and is just like holding down the reset button for a few seconds.

@anirudh_anil

Then the built-in led started pulsing (fading then getting brighter).

Yes the processor is looking for a port to connect to. You can select the correct port using the tools menu at this point.

@anirudh_anil

but when I clicked serial plotter from the IDE the board gets disconnected from the device

What IDE are you using? Try 1.8.19