It may sound basic, but please check!
There must be no errors that can't be cleared from Unity's Console window (, CtrlShiftC).
Take extra care ensuring that logs are not disabled using the toggles in the top right of the window.
Also ensure you are not in Play Mode.
Resolve errors from top to bottom. Unity can't recompile the project with errors that can't be cleared from the console.
Changes to your scripts will not display if this is the case.
If your method still isn't appearing, check that you are looking at the correct component, and try restarting the editor.
If you are seeing MonoScript-related functions, follow these steps.
Unity, huh, how?