Under Show these items on the desktop ... ve tinkered with your Finder app settings, your Mac may not be identifying your USB flash drive or external hard drive because of some random glitch.

(dot) At times, even if the memory of your USB drive is almost full, it may not show any data. So, if your USB drive is not showing files and folders in Windows 11/10, it could be either because ...

Sometimes, when you attempt to format a USB or an External drive ... folders in other parts of the computer. If your flash drive isn’t showing or displaying the space as advertised, run Bootice ...