Hi,
There is a recent bug whereby the resource group name doesn't get updated properly. Please follow instructions below that will allow you to complete the exercise.
Please navigate to Create custom routes exercise, Activate sandbox, review permissions, accept, etc. When you see Welcome to Azure Cloud Shell message appear on right, click the Unit 3 of 7 dropdown at the top to navigate back to Unit 2 Identify routing capabilities of an Azure virtual network.
Once Unit 2 page has loaded, immediately click the Unit x of 7 dropdown again to navigate back to Unit 3 Exercise - Create custom routes.
Verify in the code blocks that the resource group name as changed to something similar to learn-3294a2f5-b8ec-2def-ca62-49e23701bd77 instead of [sandbox resource group name].
Complete the exercise by following instructions, click Copy button in upper right of each code block and then right-click--Paste into Cloud Shell window on right, etc.
Please click Accept Answer and upvote if the above was helpful.
Thanks.
-TP