I have a PA-4020 that I messed up the configuration on, and I am trying to do a factory reset. I went ahead and ordered a few different serial to USB cables, and cannot connect through a Mac App Called Serial, PuttyTel (Windows) or Mac Terminal. I set it to the palo alto recommended settings of https://live.paloaltonetworks.com/docs/DOC-2124 , but still can't seem to connect. The USB device is detected, and the terminal opens without error, but you can't type any text or see anything. I have tried rebooting the router several times. Is there any other way to do a factory reset without the serial interface? If not, what am I doing wrong?
When troubleshooting anything with serial connections, try a null modem cable. You mentioned a Startech USB to null modem cable, which makes sense, but you could also have gotten a null-modem adapter, in DB9 or 25 and whatever gender you needed.