I have done jumper cut from 5v to 3.3v. I uploaded the sketch using 3.3v 8mhz as processor and lost connection. When i connect to pc, the LED light is working. There is no usb connection sound or notification and no more comp connection on device manager. It seems like reset button is not working. So i tried to connect arduino uno to micro pro to burn the bootloader, but it is not working… and says failed to connect avrdude.
Any helps to overcome this situations?
That’s the issue. When you change the jumper it doesn’t change the clock speed so you have to continue using the old board definition.
Put the original bootloader on and you should be ok. If not, follow the directions in the guide for recovering a bricked board but always use the 5 volt board definition in arduino.
Thanks!
but I tried to connect with the pc, it does not make USB connection sounds… and I cant even find the COM port 
There a procedure for this condition in the tutorial.
How to Revive a “Bricked” Pro Micro
It’s difficult to find the correct documentation right now because, for some reason, Sparkfun decided to go live with the new website CMS without fixing the internal links first.
The procedure darrellg linked is your solution, you do need to connect a button to the board though. It’s tricky to get the timing right so keep trying if it’s not working. You only have an 8 second window to apply the fix.
Sparkfun, you really need to change the bootloader to eliminate the 8 second window and make it either much longer or indefinite. It’s super easy to brick these boards and not easy to recover them.