Windows has in-built hotkeys shortcut to rotate the screen display in any direction. Sometimes like when a cat jumps on the keyboard or otherwise we accidentally activate these hotkeys and screen goes upside down.
Fix Upside down screen
It is very easy to restore screen to its normal position. Just use any of the following key combination to rotate screen to different angles and bring back to normal position.
Alt + Ctrl + Top arrow key
Alt + Ctrl + Bottom arrow key
Alt + Ctrl + Right arrow key
Alt + Ctrl + Left arrow key
If above does not work, right click on empty space on desktop screen, goto graphic options > Hotkeys > Enable. Now to revert to normal screen display, select rotation under graphic options and click on normal option. This should bring screen back to its normal position.