I am not sure why but my Apple ID or Garageband was not asking for a password. Happened on all three of our computers.
We did find clicking on the box in the upper left corner, maybe it is the library whatsit. Looks like one of those in-out boxes back in the day when we had offices and paper. ;-)
So once they asked for the password, downloaded just fine.
This computer mentioned in the title here took clicking on that box before it requested a password. I even went through a threw out Garageband and all its parts, then reloaded fresh.
My wife's computer sat for a bout 15 minutes and suddenly popped up the request and our Mac mini, slowest computer of the bunch took only 10 minutes.
So for anyone who has this problem, if Garageband has not asked for your main password so it can load new software, that is the problem.