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.

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.