When we upgraded FW, WAN port was not functioning. Matt supported us by remote PC control and solved the issue. Tank you.
Summary 1) Remove power cable first.2) Press the reset key and plug the power cable while reset key is being pressed for more than 8 seconds. 3) login with 182.168.1.1/index.html 4) special screen upload FW.
When doing the FW updated by web, untag keep all setting.