After physically connecting your HP scanner and installing some software, your computer recognises that scanner in ‘Device Manager’ but an HP software fails to connect to that scanner. Try installing that hardware first before installing that HP Scan software. You can try unplugging that device from a USB port, then uninstalling that software from add or remove programs in control panel.
After that software and device is unplugged go to control panel again and this time select device manager. Once in device manager highlight and right click to delete that scanner from device manager. Plug back in that scanner via USB and Windows should detect that scanner again.
It should prompt you for a driver CD. Insert that CD-ROM and then select a CD-ROM check box. Click on Next and those drivers will install.
That HP scanning software installation should begin after those drivers are installed. Go ahead and install that HP scanning software. Hopefully, that scanner will work this time.
Check out these hp document scanners instructions, plus some other troubleshooting steps.