Indicators - unselectable

 
Indicators -> Custom -> ZigZag can not be selected. I have tried deleting ex4 files and reloading MT4 to no avail.
 
Right click on custom indicator on Navigator Window and select "Modify". Then programm MetaEditor will appear, and press F5 to compile open source of custom indicator.

Did you see "MQL4: Secrets of MetaTrader 4 Client Terminal" ?
 
Thank you Rosh for showing me an alternate way of calling up indicator, however if trying to select the indicator via the main MetaTrader desktop from the "Indicators" icon (situated between the "Chart Shift" and "Periods" icons) then the indicator "ZigZag" is unselectable from the menu Indicators -> Custom -> ZigZag as well as four other indicators.
Reason: