Hi,
In the exercise, please use command similar to below to create the key vault. You need to substitute the correct sandbox resource group name for [sandbox resource group name] and enter a unique vault name:
az keyvault create --resource-group "[sandbox resource group name]" --location centralus --name <your-unique-vault-name> --enable-rbac-authorization false
The above command will create the Key Vault with permission model set to Vault access policy and grant your user account permission to perform necessary operations. In this way when you execute the command to create secret it will succeed.
Please click Accept Answer and upvote if the above was helpful.
Thanks.
-TP