Hi,
You can workaround the issue by first Activating the sandbox (solving puzzles, reviewing permissions, etc.) and then once you see the sign-in box appear on the right open a new browser tab. In this new tab, browse to https://shell.azure.com.
When prompted, click Bash.
Next choose No storage account required, for Subscription select Concierge Subscription, and click Apply.
After several seconds delay while a cloud shell is requested and connected to, you should see $ prompt. At this point you can complete the exercises instructions, copy/paste code from exercise tab to cloud shell tab as needed, etc.
NOTE: You need to first redo Exercise - Create an Azure virtual machine and then jump to Exercise - Configure network access and complete that last using the same active sandbox. Keep the same extra browser tab open with cloud shell and use it for both exercises.
Please click Accept Answer and upvote if the above was helpful.
Thanks.
-TP