https://devzone.nordicsemi.com/f/nordic-q-a/15620/ld5-flashing-quickly-board-not-visibleHi, I have been working with my nrf51 DK for a while now without problems. When I first connected the board to the computer today, the ld5 led was blinking very quickly, and the board was not visible anymore. I have tried the tips in this thread: en-USTelligent Community 13Mon, 29 Jul 2019 23:12:24 GMThttps://devzone.nordicsemi.com/thread/201079?ContentTypeID=1Mon, 29 Jul 2019 23:12:24 GMT137ad170-7792-4731-bb38-c0d22fbe4515:eca4acd3-68ec-417d-bb04-d4e2781e3698Berry Blue<p>Is this available for Mac?</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/190085?ContentTypeID=1Thu, 30 May 2019 15:17:29 GMT137ad170-7792-4731-bb38-c0d22fbe4515:4374c348-8da3-4d02-bdad-1c824b38fc49sajingeo1<p>Sometimes the micro USB connector pins lifts off the pads you could try to solder it back or try a different USB cable.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/59610?ContentTypeID=1Tue, 09 Aug 2016 09:32:01 GMT137ad170-7792-4731-bb38-c0d22fbe4515:adf8a0f9-670e-45b3-a67a-06cf2fb1970dLene<p>The board became visible in bootloader mode after changing to another usb cabel, so the problem is resolved :-)</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/59609?ContentTypeID=1Tue, 09 Aug 2016 07:42:46 GMT137ad170-7792-4731-bb38-c0d22fbe4515:8bd514c3-9412-4bd2-8ea5-71896414a5d8Susheel Nuguru<p>open J-Link configurator and if you see your device then you can reflash the segger firmware into it. I am not sure what you can do if you cannot see it here.</p> <p><img src="https://devzone.nordicsemi.com/cfs-file/__key/communityserver-discussions-components-files/4/5756.Capture2.PNG" alt="image description" /></p><div style="clear:both;"></div>