Only other thing was changing out the cat-5 cable from the P2 to the network switch, and changing the port on the network switch it is connected to.
That and the reset of the PLM.
Other than that, everything is the same.
That's great news!
My money's on the PLM reset as as it's a well documented solution among Insteon users. It's analogous to clearing the CM-15A when repurposing it for the PiX10Hub. If you were able to connect to the P2 from the app before switching the cable & port, that was not likely the problem. If it was, it wouldn't have been solved by just unplugging the USB cable. I'd just take what is hopefully the win and move on but if you want to pin it down you could put the old cable and port back in play and evaluate.
A word about Insteon PLM's. In addition to the 2412U there is also a 2413U version that adds Insteon RF (NOT X10!) to the mix. I use that because I added an Insteon RF Open/Close Sensor to a package drop box so that a delivery triggers a text message, flashing light and chime. The 2413U has a high failure rate, unlike the 2412U which is rock solid. The fix is to replace the 7 electrolytic capacitors with more robust values. Mine failed on Saturday. Knowing that eventually it would, I had the caps on hand and it's back in service.