nRF51 doesn't show up anymore aftering bootloader mode

Hello,

After (accidentally) entering bootloader mode on my nRF51 DK (PCA10028), the device doesnt show up either in the device manager or using nRFgo Studio (both not normally, as being in the bootloader mode where LD5 is blinking.)

In case I turn the DK on and off normally (without pressing the reset button), the LD5 doesnt blink or turn on otherwise. If I turn the DK on while holding reset, BOOTLOADER shows up as a USB device, and the LD5 blinks.

Can anyone help me out, thanks in advance.