NSX-T 3.X or NSX 4.X
In order to remove the entry use the following API calls:
Once completed, refresh the UI to confirm removal of the AD entry.
Alternative options to resolve the issue is the attempt to stop the sync is to use the below POST API call:
POST https://{nsx-manager-ip}/policy/api/v1/infra/firewall-identity-stores/{firewall-identity-store-id}?action=STOP_SYNC
After, check if the UI allowed delete of the AD entry. If not, complete the above DELETE API call.