I did eventually find my own answer. I figured out you need to point it to the My Paratext Projects folder, not to the actual project within the folder. On the computer I was working with, this folder was in the root directory. Because I had pointed it to the wrong folder initially, I ended up needing to go find the configuration file and manually edit it. I found it by searching from the root on PTXprint. I no longer have access to that computer, having returned it to the owner and don’t remember exactly what the path and filename are.