If the auto unit went off, you'll need to take it off before the pin will retract - the spring will hold it out. Once the auto unit is off it should go straight back in. If it won't retract when you've taken it off, then try the manual lever to see if that moves it in and out.
If it still won't retract - the mechanism might be knackered - so you might need to go and get professional help!! I've never had this happen on any of my jackets - but there'is always a first time...
D...