Make sure you have your lcd plugged in correctly, iirc there are three spots to plug in the LCD and only one works.
As a complete workaround you could install something like octoprint on a raspberry pi or another computer and hook up the printer and confirm you can control it via the webpage.
I love this. When we were actually using that type of modem as a daily driver we only dreamed about object replicators or using a computer to make physical objects with additive manufacturing at home! This is an awesome bridge to the past.