Press Ctrl + Spacebar to toggle between the US keyboard and the INTL keyboard settings.
A Chromebook sometimes says "INTL" on the bottom right, instead of "US". When you see this, it means the Chromebook Keyboard has been changed from the US Standard keyboard to the International keyboard. When this happens, some of the keys will not make the symbol you expect to appear (like the apostrophe).
Although this can be done intentionally, it usually happens by accident when Ctrl + Spacebar are pressed.
To change the Chromebook keyboard back to US settings, press Ctrl + Spacebar again. This keyboard combination is used to switch back and forth between US and INTL keyboards.