I’m not a Logic user normally, but I also struggled using the example Logic file as I also run at 48kHz. It was much easier for me to start from scratch.
Problem 2 is I don’t think the current instructions are complete if you want to record. Yes, you can get audio coming into the track, but Logic is recording the track input device, not the output of GP Relayer. To record GP Relayer, I needed to route it to a Bus, and then have a second audio track that had this Bus set to be the track input.