Dunno how the factory setup works as far as what makes lights blink, but I swapped an e-locker rear into my 01 and a lot of the time the locker won't engage until the rear wheels have turned at different rates. In other words, it takes a tight turn or one wheel spinning slowly with the other stopped until the locker will engage.
Maybe try that? Could be your actuator is functioning, just weak from non-use over the years.