Connecting WebControl to Arduino

I’m using a Metal Maslow and have driven it with a MacBookAir 7,2 using a Ubuntu 24.04.5 LTS and WebControl v0.94. I am now trying to operate the Maslow with a Lenovo ThinkPad P50 also running the same Ubuntu OS. I attach the USB from the Maslow to the ThinkPad, launch WebControl (also v0.94) and under maslow settings I refresh the list of serial ports and choose /dev/ttyACM0 and use the submit option but the display still shows not connected. Specifically “Connected to 127.0.1.1:5000 CPU 19% Not Connected” with Not Connected in Pink. In Terminal I can see the Arduino SA mega 2560 R3 (CDC ACM) Bus 001 Device 016: ID 2341:0042. Since the list of serial connections populated it seems there is a connection between the WebControl and the Maslow. So how do I connect?