I'm a newbie to nRF5... I just installed latest IAR, nRFgo, Segger J-link & nRF Connect on Windows-10. Segger J-link appears to have updated nRF51 Dongle to 6.3. I get the above error message after launching nRF Connect v2.3.0 and selecting the dongle's COM port. Any help would be appreciated.
I eventually figured it out on my own. It wasn't clear by the error message what facet of the dongle was the issue.
Was USB memory protected?
Was it something to do with the Segger J-tag?
D'oh! neither - the nRF51's code space readback was locked-out and nRF Connect apparently needed to re-program it.
I think I ended-up used nRF Studio to full erase the target nRF51 on the dongle and everyone was happy after that.
Great! Thanks for sharing the solution with us.