Welcome to YamahaSynth!
It is customary for help with computer related issues to provide the computer type and operating system. This will help determine which Yamaha USB-MIDI Driver version you need to install. The computer will not necessarily recognize the synthesizer without the proper driver installed. It’s all a matter of matching computer, operating system version, with the correct driver version.

Also the firmware version of your MX may need to be updated. The instrument has specific error messages. Those messages appear when a query is made and something does not meet the requirement. Try to quote exactly the error message; it helps pinpoint the exact problem and please indicate where the error message appears, the computer or the keyboard. The handshake, if attempted and not made successfully, causes a specific error message.