Hi,
Please repeat the exercise from the beginning, only this time substitute below command for the one in step#3:
az keyvault create --name $myKeyVault --resource-group az204-vault-rg --location $myLocation --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