If you have issues (empty folder, cannot connect, etc.) when connecting your Xiaomi phone to your PC via USB cable, you should try the following before you try anything else. This is how I solved it after I installed Mi Suite and enabled developer options and USB debugging; these were not necessary.
- Connect your device to your PC.
- Unlock your device (phone) if it is locked.
- On your device, swipe down from the top of the screen.
- Scroll down if necessary until you see the notification of the “Android System”. It should be saying something like “This device is charging from USB”. Click on for other options. Choose file transfer or photo transfer.