Hi,
I’ve asked for replacement Teensy Arduinos, I’m not sure if they will be here before class on Thu.
Please work on getting p5.js talking to your Arduino. I have mine working on Win10 without NPM. Here’s simple sketches for p5.js and Arduino. Remember that you have to disconnect p5.serialconnect before you can upload and Arduino sketch. On your browser (I use firefox), you might need to shift-reload the p5.js sketch to get it working again.