Android Pie only showing two folders to Android File Transfer
I have some tips for you to get it working because Android 9 lacks the notification popup which asks to select between modes(File Transfer, MIDI, PTP, No data transfer, Charging,etc.) when you plug your phone to your computer via USB.

You can try the following things:


Enable Developer Options.
Enable USB debugging.
Try changing USB port on your computer in which you are plugging your phone.
Make sure you are using data cable and not the charging cable.
Go to USB Default Configuration in Developer Options, there you will see different modes(File Transfer, MIDI, PTP, No data transfer, Charging,etc.) to choose from.
After selecting 'File Transfer', unplug and plug your phone again.


For more details, visit the link below: https://youtu.be/l8jP8YxDL5w