Hi Erwan,
Quoted from coursera:
You’ll only be able to access your Coursera Lab assignments and Jupyter Notebooks if you have a paid Coursera membership. If your subscription ends, you’ll be put into audit mode and won’t be able to access them
If you have a valid subscription to the course in question but you are not able to access the labs, you may check this post out and try step 2. If step 2 doesn’t work, I am afraid you will have to contact Coursera to look at your account.
Raymond