Follow these steps to configure your android device to android studio:

• Disconnect the USB from the device.
• On the device, go to Settings -> Developer Options, and click Revoke USB debugging authorizations.
• On the device, go to Settings -> Storage -> USB Computer Connection (available on the drop down menu at the top right of your screen). Verify that Media device (MTP) is CHECKED.
• Reconnect the device, now everything should be fine