In this particular case, the player forgot to expand the company. The issue is the interface does not make that clear. It displays the prompt once, but if you refresh the browser, etc. it does not display the prompt again.
Generally, selecting the "Undo" button resets things allowing you to re-enter your move and resolve any issues. For example, in the above case, undoing and re-entering your move would display the prompt again, letting you know that you need to expand the company.