What USB mode is it in? Typically, the default is Auto Detect, which can be problematic. Try manually selecting MSC mode & check; the player will show in File Explorer as 2 new separate drives (player & SD card slot).
If this doesn’t work, detach from the computer and select MTP mode & try that. Note that if either of these settings allow you to see the player, you still may not see the content (files) as the player needs to be connected in the same mode as it was when the files were initially transferred/copied to the player in order to be seen.
Hence the problem with Auto mode.
