Many devices go into special USB modes without any indication on the screen or sound.
Especially in Windows this is a problem because missing drivers complicates things.
UsbView is an ancient (but still useful) utility from Microsoft.
https://ftdichip.com/wp-content/uplo...07/usbview.zip
You can see if your device is connected and what interface(s) it is presenting.
At the basic level, you can disconnect and reconnect your device and see if Windows "bongs".
If something is there, you need to check what it is and if it needs some drivers.
If you have a Linux computer around it's easy to just plug something in and then look in "dmesg" to see how it connected.
Finally, if you have a console UART connected, most (but not all) things will tell you what they are doing.
(Disclaimer: I know nothing about RockChip. Did anyone mention what VID/PID the Loader is?)