Why can’t I login to my Adtran router’s admin page?

I want to make a Minecraft sever via my router. I have done this before in the past, but I cant connect to my routers admin page. I have tried resetting the router (Adtran, which is also connected to a modem). I have unplugged the modem and waiting 30 seconds then plugged it back, resetting it, and that did not work.

I have disabled all firewall protection and anti-virus protection. I know that the Default Gateway is http://192.168.40.1/. I also have tried connecting through the windows control panel by going to my network and selecting the router which is called “ubuntu router”. I have reset my computer. The issue with connecting an ethernet cable is the fact that I dont have one, and all of the lan ports are connected to something in the wall (these lan ports are on the modem.)

I honestly have no idea what to do, because I have also tried connecting to the admin page via other computers and it doesnt work. If a run a windows diagnosis it states that I am connected to my wifi. What should I do?