ok, it seems to me that you have to access the unit wirelessly to enter the LuCI. You first have to disconnect the TIU cable/wired network cable to isolate the unit. Then look for the wireless network MTH_DCS-XXXX. Join that network. Then type the 192.168.143.1 into your browser.
Page attached. Change the title of your post to get Barry and the other guys to see your problem. can't connect to WiFi LuCI