ESX 5.5 cannot find iCSSI Target on Synology NAS

Hello

I have problem with  Vsphere 5.5 connecting to iSCSI target i have created on Synologay NAS DSM 3.0

- Within my LAN at Home, (a homelab)

- I have successfully created a Target on Synology DSM 3.0. Service Status = Ready

- In Vsphere 5.5 WebClient,  I add iSCSI Server. e.g. NAS1.mydomain.org at port 3260

- Rescan storage.  I cannot find the new Storage device.

Please help or hint me where can I get more info to fix this issue

Thanks in advance

MinhPham