MT5 New Order F9 Not working

 
Need help please. I am in a trade and have placed a market order. Subsequently I wanted to add a Stop Loss and Take Profit orders but it is not funcioning. Have restarted the and re installed MT5 but still not working on live or demo accounts?
 
I just checked - F9 is working for new trade on my MT5 (build 3802 on Windows 10 64-bit computer).
If I want to add stop loss or take profit to already opened trade so I use mouse:
right mouse click on the trade in Toolbox - Modify or Delete