I've had it four times and never gotten it to open until week out. I could book all summer long a week out even though my reservation is August. I even got an email invite this time and still hadn't unlocked my trip time. No rhyme or reason.
It will NOT show on FP+ or MDE, you can only see on BOG page you book on. Suggest you print out copy.
Not sure when you are coming but we were at MK on Saturday and were able to walk up at 11am and there was no line. Coming out around 11:45am there was a line up to down way half the bridge so it still wasn't bad.