USB updating requires Chrome or Microsoft Edge on a desktop computer, over HTTPS.
Preferred method — Update via USB
Connect the PC/Power USB-C port on to your computer.
Press
…and select the USB connection.
Loading updater…
Firmware download: not started
Flash programming: not started
USB connection / update details
If you have trouble connecting:
Close Arduino or any serial monitor, disconnect the USB cable, reconnect it and select INSTALL again.
Try again using the correct USB connection.