Most likely you don't have a working connection between your radio and computer. For example, if you leave the programming cable unplugged from the radio and attempt to download from the radio, is the error message this same? If yes, then this is most likely not a CHIRP issue.
Does your programming cable work with the factory programming software? If it doesn't either, then that is a very good indication that you have a programming cable/driver/port issue.
If your programming cable has a Prolific chip inside, have you downloaded, installed and selected the older Prolific v3.2.0.0 driver? The driver automatically installed by Windows does not work in most cases and the older driver is required. The Miklor.com website has links and instructions on "this page":https://www.miklor.com/COM/UV_Drivers.php.
If your programming cable has a WCH CH340 chip inside, Windows often installs the incorrect driver. The workaround is to download and install the latest one from the chip vendor's website.
It is unclear which model you really have (qyt8900 doesn't appear to be valid). I could be KT8900, KT8900R KT8900D, etc.
Jim KC9HI
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