jaredwolff I’ve never seen an error like that with nrfjprog. If you don’t connect the Tag Connect, does it work with the nRF53 ok? My nRF53DK is very flaky and essentially stopped working after many hours of work. Did you modify the DK at all?
The strangest part is that the blinky code I programmed last time is still functioning. When I connect the nRF5340 without the J-Link being attached to the Feather board, the SDK Connect Programmer App recognizes it as an nRF5340DK (see slide 8). However, as soon as I connect the J-Link to the Feather board, the SDK Connect Programmer App no longer detects the nRF5340DK and only shows the J-Link (see slide 8).
I did not modify the dk but I am sure nRF5340dk detects the board is connected via P19, because without connection app recognised as nRF5340dk and with connection with feather board it does not recognised as DK
I have three new nRF5340 DK boards and I tested 02 and getting same issue. I need to order more boards but waiting to resolve this issue because I already designed PCB as per Feather board pinouts