Custom indicator not showing in MetaTrader 4

What is causing it

The .ex4 or .mq4 file is in the wrong folder, or it needs a recompile.

Why this happens

MT4 loads custom indicators only from inside its own data folder, which sits in your user profile rather than in the program installation directory. Windows separates the two so the terminal can write without administrator rights, so a file copied into the installation folder is somewhere the platform will never look. The Navigator shows what was found when the terminal started, which is why a newly added file does not appear until you refresh it.

MT4 runs the compiled .ex4 file, not the source .mq4. Having only the source present, or having a source file that has not been compiled, leaves nothing for the platform to run even though a file is visibly sitting in the right folder. An .ex4 built for a much older or newer build can also refuse to load, in which case you need a current version from whoever supplied it.

The fix, step by step

1. Open File, Open Data Folder, MQL4, Indicators, and confirm the file is there.
2. In the Navigator, right-click Indicators and choose Refresh.
3. Drag the indicator onto the chart again.
4. Restart MT4 so it recompiles.

How to confirm it is fixed

Right-click the chart and open its list of applied indicators. If yours is named there it attached successfully and any remaining issue is display or settings. If it is absent, it never loaded, and the Experts tab will usually record why.

Stopping it happening again

Install through the data folder opened from inside the running terminal, never by browsing to a remembered path, and refresh the Navigator straight after copying anything in. Keep to one MT4 installation per broker you trade, because a second copy has its own data folder and cannot see files placed in the first.