A custom or third-party indicator will not load in Quantower

What is causing it

The file was not placed where the platform looks for it, it was built for a different version, or the platform has not been restarted since it was added.

Why this happens

Custom indicators are compiled code loaded at startup. If the platform cannot find the file, cannot load it, or finds two conflicting versions, the indicator simply does not appear in the list.

Version mismatches are the most common cause with third-party tools, because the platform's interfaces change between releases and an old build can stop loading after an update.

The fix, step by step

1. Follow the vendor's installation instructions exactly, since the correct location for custom code is specific to the platform and not somewhere you should guess.
2. Restart Quantower after adding any custom indicator, because it loads them at startup.
3. Check whether the vendor's build matches the version of Quantower you are running, as an indicator built against an older release may not load.
4. Look at whatever the platform reports when it fails to load an indicator, and pass that text to the vendor rather than paraphrasing it.
5. Remove any older copy of the same indicator before adding a new one, so two versions do not conflict.
6. If it is your own code, build it before expecting it to appear, and fix any build errors first.

How to confirm it is fixed

The indicator appears in the indicator list, adds to a chart, and can be configured without an error.

Stopping it happening again

Keep the original download from the vendor, note which platform version it was built for, and re-check after any platform update.