Unable to delete BizTalk Services Artefacts from the portal
To resolve the issue, go to https://resources.azure.com/ Go to particular subscription => resource group. Find the artefact and do the delete operation.
To delete Access Control Namespaces
Log in to the old portal
From the left navigation pane, select Active Directory
On next page, go to Access Control Namespaces
You should find your ACS namespaces over here and be able to delete those.