Ah, sorry I didn't notice it was version 1.2.0 installed and not 1.12.0. Version 1.2.0 is really old and does not support USB HID flashing or automatically switching to bootloader. That's why it won't let you immediately flash the AudioMoth. You need to click on the link that says 'Follow instructions to manually switch to serial flash mode' and follow the instructions in the pop-up window that appears. Make sure you cycle the power on the AudioMoth - unplug and plug back in without batteries - after this update.

With version 1.12.0 of the firmware, you can also update to the Config App to version 1.13.0 to use all the new features of the firmware. It will still work however with the current version of the Config App that you are using.