I can't finish an exercise

The 'Finish' button is grey and unresponsive.

You probably haven't answered all questions in the exercise. Go back and check all the questions.

I don't see the 'Finish' button

If you don't see a 'Finish' button, this is most probably due to your screen size or resolution. The best solution is to zoom out slightly using the key combination CTRL + - (Windows) or CMD + - (macOS).