Thank you! It works now.
Seems like password was automatically restored when a static IP on PC matched IP range on the LinkStation, thanks to your advice.
- connect device directly to PC
- set a static IP on the PC to match IP range on the Linkstation
- refresh the device on Nas Navigator. The Linkstation and PC is successfully connected.
- open the Web UI, admin username and password is prompted. Not certain whether it is admin default password or not.
I leave it as it is and hit log in button right away
- disable DHCP to modify invalid IP to match IP range of current ISP then save
- on Linkstation Web UI, enable DHCP and save
- on PC, enable DHCP
- connect the Linkstation to router
Many many thanks to you all.