After the activation or the reset of your Shadow, you can have the following Windows error “Windows could not complete the installation. To install Windows on this computer, restart this computer.”:
When we create or reset your Shadow, a system preparation (also called by the little name of “sysprep”) is performed. In our case, the sysprep failed and we didn’t detect it automatically.
The workaround is to perform another reset after the failed sysprep, from https://account.shadow.tech/myshadow.