"This item will be unlocked when the session begins"

I am having the same problem, have you figured out how to deal with it by any chance?

I'm having the same issue, and the article in the Help Center does not really answer the question - is it because we are still in the trial period? On the course page, it says:
"What do start dates and end dates mean?
Once you enroll, you’ll have access to all videos, readings, quizzes, and programming assignments (if applicable). If you choose to explore the course without purchasing, you may not be able to access certain assignments. If you don’t finish all graded assignments before the end of the course, you can reset your deadlines. Your progress will be saved and you’ll be able to pick up where you left off."
I have already put my payment information and I want to continue with the course this week that I'll be on vacation.

I am having same issue.Can you solve the issue at earliest.Why it is locked ??

This item will be unlocked when the session begins.

This session has not yet started. You may access this item after the session starts on 9 September."

What to do??

I solved my problem contacting the support by chat (you can find it in the Help Center). They have put me in a previous session, where I could already access the assignments.