Hello,
@campa and @Michael_Gordon You need to delete all the files from the file section and then retrieve a fresh copy. Probably you are missing some of the steps. Please have a look at the below post.
@TMosh Kindly guide them if they have confusion about the same, thank you. They need to update the lab or get the fresh copy of the latest version of notebook as we discussed just a while ago. Make sure to save a copy of your work before you follow the below post.
Also understand that once you have latest version, you need to again manually write the codes.
Let us know if the issue still persist!!!
Regards
DP