I would try other keys first, especially the RED one, could just be the chip has gone duff in the key.
My dads mk1 mondy led light does not work as it should either staying lit for 5 seconds after it has started but always starts first turn.
Another thing to try is rub the key with a wet cloth to discharge any static, as a build up can stop the key being recognised, if all keys don't work it would more likely be the receiver around the ignition barrel than the keys or immoby at fault, so a scrappie receiver should soon tell you if it is that.
tabetha