Try a different USB port or reinstall the VCOM drivers.
on your Windows PC to ensure the device is recognized in "Preloader" mode. Battery Charge acer one 8 flash file
A "flash file" for the Acer One 8 (tablet/laptop family—model specifics vary) is a firmware package that contains the device’s operating system image, bootloader, recovery, and partitions needed to reinstall or restore the device to factory software. Flash files are used to: Try a different USB port or reinstall the VCOM drivers