Thank you for the additional information. Some USB cables are only intended for charging and not data communication, which can cause that kind of error. Could you try some different USB cables (preferably ones you can verify work for data transfer with another device)?
By the way, I’m not sure why you see both the 3pi+'s regular USB port and the bootloader port at the same time. Did you ever try using the “Add Legacy Hardware” option in the Device Manager in an attempt to get the board to be recognized? This option is only for older devices that do not support Plug and Play and could cause some problems. So, if you did try doing that, could you follow the instructions David’s post here to remove those non-working entries and see if it helps? That post is about the Maestro, but it should be the same process for an A-Star.
Brandon