Can't program nrf51822

[yokay]

After program nrf51822,it works normaly.But when I program again,it can't debug.NO SWD and NO USB DEVICE.So I can't use nrfGoStudio or nrfjprog.exe to recover it.When I pull down the SWCLK/nRESET pin, I can find the SWD, but no device serial number.Please help me.Thanks very much.

[yokay]

I found the solved ways.In my schematic , there is a hardware error.The VCC was pulled down.So I can not program.