Hi,
Since many hours have elapsed since you wrote your question, please open a separate tab, navigate to the previous module's exercise, click Verify, solve puzzle, review permissions, allow, solve puzzle again, etc., until Azure Cloud Shell window is displayed on right.
Complete the exercise again even though you likely completed it previously. This is a new sandbox so any previous files/work from when you did the exercise before are gone.
Once you have re-completed the above exercise, please navigate to Exercise - Start a project in a separate tab. You can switch back and forth between the two tabs as needed to complete the exercise.
If you accidentally close the tab that has cloud shell, you can open a new browser tab and navigate to https://shell.azure.com . After the cloud shell is displayed, please make sure in upper right that it says MICROSOFT LEARN SANDBOX under your account name. This assumes the sandbox has not expired (previous sandbox should be valid for 2 hours).
Please click Accept Answer and upvote if the above was helpful. If something is unclear or you still need assistance please add a comment below.
Thanks.
-TP