My pixhawk 4 is not stay connected with my pc during firmware uploading, it outs and in to USB port when i look to device manager

I am facing a connection problem to my pc even after installing all required drivers
my problem is ----------------------
when I connect my pixhawk 4 to the computer the USB sound is out and in always and when I see it in device manager the USB is in and out in the port section. it does not stay.
this happens when I upload the firmware for the third time, the first time it worked correctly

please, anyone, help me it is my new brand flight controller and I want to use it to try the new control law for my master thesis.