Hi @Ted_Finch, you need to enter the bootloader mode by sliding the power switch twice quickly and An external drive named Arduino should appear in your PC. Drag the the downloaded rtl8720_update.uf2 files into the Arduino drive and it will reset the Wio Terminal and loaded loaded the sketch!
Then Try to flash with the CLI tool.
more details : https://wiki.seeedstudio.com/Wio-Terminal-Network-Overview/