Hello,
I notice you are using a standalone segger debugger with a pretty old FW version (dated 2014). Maybe it's too old. Have you tried to erase the chip via other programs such as J-link commander?
Yep, nrfjprog works as well, however I’ll update fw thx
Thanks for confirming. Turns out it's probably not an issue with your debugger, but a bug in our latest version of the Programmer app (1.4.9). Several others have reported the same problem now: https://devzone.nordicsemi.com/f/nordic-q-a/75922/firmware-update-impossible-using-nrf-connect-v3-6-1
