@jay_s_uk
The SD card does not have the firmware folder to put the file in.
I can create the folder, but does the fact that the folder is missing mean that the upgrade from 3.0 to 3.4.6 was not fully successful and that other things are probably wrong?

This is what the SD card looks like.

I had to replace my board. Duet 2 wifi.
I successfully configured the new board to talk over wifi.
I updated the firmware from 2.x to 3.x then finally to 3.4.6 - where I needed to be for my modix printer.
Now the wifi does not work and I get the error:

Error: M997: File 0:/firmware/DuetWiFiServer.bin not found

When I try to flash it.

How to I get that file and install it using the USB connection to the board?