Hi @Ironclad!
The most common reason for this is folder structure, double check that it is like this
My other thought is that unlike with Arduino boards, the Blink won’t show up in the list of USB ports. This is because we are not programming over serial, we are using an ISP to flash the hardware. So no need to select port when uploading, just the correct programmer.
Let me know if that does it.
Best,
Jb