I have tried several cables and laptops, and rebooted.
the port does not show up anymore. and I get no USB audible badoop sound when i plug in.
if I enter bootloader mode, it does show up as a flash device.(and the sound)
I see instructions about copying a UF2 file but I must be doing this wrong because it isnt working.
but how could the blink program be preventing USB comm?
is there a way to just factory reset?
There are 3 modes for that board, you might want to perform a factory reset and start over https://learn.sparkfun.com/tutorials/sp … bootloader
as there are some caveats to each mode 
(basically, you may/may not need to use the buttons depending on your choices)
I ended up doing the bootloader reset and uploaded an empty program but had to compile it using an old version 0.21 of the nef adafruit board.
Now it works fine.
This setup seems flaky as the blink program seemed to compile one day then not the next.
Now for a post on another board, my son is trying to use the alternate board manager but the nrf adafruit board is not presenting as an option
