Your example doesn't work in your application. Why?

This has been happening to me a lot lately.

This is your example. You wrote it for me to use in your application. It compiled, but it failed the test. Why? How do we fix it? Do you have to fix your posted code, or do I have to fix something here?

In Arduino, I've seen scripts lacking void loop() raising this error, so I inserted app main(), but it did nothing. I have PlatformIO running.

[screen grab of VSCode][1] [1]: https://ift.tt/3grHhtb

Your answer is going to be important, because I have to understand how to translate Arduino into C++. I don't really know how to do proper C++, because Arduino is not strict C++.