Hi,
The sandbox expires 1 hour after you activated it, and anything you created is automatically deleted. Please Activate a new sandbox, and before you try to run commands, make sure that the code in the exercise has the correct resource group name.
For example, instead of the code saying [sandbox resource group name] it should have something similar to learn-3294a2f5-b8ec-2def-ca62-49e23701bd77. If it doesn't have correct resource group name, please navigate back to previous Unit using dropdown at the top, allow page to load, then navigate back to exercise you are on, click verify, solve puzzle, and once it says Welcome to Azure Cloud Shell copy/paste the create vm command.
https://learn.microsoft.com/en-us/answers/questions/1538922/credential-problem
Please click Accept Answer and upvote if the above was helpful.
Thanks.
-TP