USB Imaging Tool ThinOS 9 Wyse 3040

Hello everyone,

We would like to set up a Wyse 3040 with ThinOS9 using a USB stick and USB Imaging Tool.
USB Imaging Tool runs correctly on the Wyse, but when the ThinsOS9 Wyse 3040 installation is started, the following error message always appears.

How can the flash be emptied? Or does this mean that no flash can be found? How can this be fixed?