You most likely had a margin call. If losses from your open and closed positions exceed your Quantfury account balance value, there will be a margin call. A red notification will appear at the top of your screen informing you of the margin call.
You can verify the positions that caused the margin call, as well as your past positions, in your Trading History:
Open your Quantfury app side menu, tap on 'Trading History'.
Click on 'Closed Positions'.
Scroll down the page, and tap 'History Previous Sessions'.