To unlink an existing/deleted PNID and to link/create a new one, follow these steps
- Open Universal Updater
- Search "luma" and download the Luma3ds
boot.firm - Still in Universal Updater, also search "Nimbus" and re-install it (no need to uninstall first)
- reboot console
- Open Nimbus and press Start to finish the Nimbus update process
- Open Nimbus again and click Pretendo
- Open Nimbus a third time and click the corresponding button to unlink your PNID
- Go to System Settings > NNID settings at the top to create/link your new PNID