Failed compilation#

Ensure that your code has actually compiled.

There must be no errors that can't be cleared from Unity's Console window (WindowGeneralConsole, 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.

Runtime exceptions#

Read all errors and warnings present in the console at runtime. Exceptions will halt execution, causing code execution to move to the first place they can be caught. This may cause your message to exit prematurely.

I am still not getting a message.