It may not be clear on the lesson. If you are reading a lesson from a previous week, you are not able to write anything in the homework questions. That part of the lessons are only active for current lessons.
For example, if you are on week 3 but reading lesson 2, you will still get credit for reading the past lesson but it will not allow you to write in homework answers. You can only write in homework answers on lesson 3, since that if that is your current lesson. The same thing applies to actions plans.