This indicates the controller did not successfully enter update mode. Unplug the controller, hold down a different button interface (try , Minus , or D-Pad Up ), and reconnect the cable. The Controller Won't Turn On After the Update
Always try this first, as some premium third-party controllers designed to mimic the Pro Controller can sometimes accept updates through the console if they use compatible firmware. Navigate to System Settings on your Switch home screen. Scroll down to Controllers and Sensors Update Controllers n-sl wireless controller firmware update