I am brand new to the JMRI/DCC++ scene, and I have started out the best I know how. Unfortunately, my excitement has far outpaced my ability, I am afraid. I have installed JMRI on a Raspberry PI 4, connected that to an Arduino-branded Mega and Motor shield. The locomotive is a simple 040 American LGB, running a 55021 chip. I put my first loco on the operating track, and Voila! It turns the lights on, it turns the smoke on, it runs forward and backward! When I impounded the loco on the programming track, and tried the single CV read function, I always get the following message: No acknowledge from locomotive (308) I cant write any CV's either. I've followed the connection diagrams found on the Git server, with the traces scratched from VIN and jumper from 2-13 on the Digital header. Have I missed something super simple?