Had this issue this afternoon where I paired the garage door sensor Linc, deleted it because I thought it would help with opening the garage (it didnt, I had wired the garage door relay wrong) and when I tried to re-add I could not for the life of me get it to pair, even though all the ISY and PLM looked to be online and when I tried to do it manually by adding the address, I got the "cannot determine insteon engine" error after 7%. This was after a powercycle of both ISY and PLM.
So my last ditch effort was to make sure it wasnt a signaling issue was to plug in the garage controller closer to the PLM. It worked instantly, by using the set button and link button. I then moved it back to the garage, and it was still controllable by the admin console without issues. Im guessing that the re-paring was failing due to some signal problem, but its not working. If it stops, Ill update, but it might be a workaround worth considering.
Aceball