I haven't posted until now as I know a number of users have been having the same issue, but I am getting really quite frustrated.
Over the past six weeks I have collected 50 green candies every Thursday and got the lollipop hammer from Dexter, but only once over the past six weeks has the space race appeared by itself.
I also regularly reach the mystery chest and music box, only to find that the keys don't appear and those challenges disappear altogether.
I saw a solution suggested on another post about logging out, restarting my device (I'm using Android) and logging back in, and the first week I tried it, this worked, with both the space race and the music box keys appearing when they had disappeared before. However, this has not worked since despite me trying it many times.
I have played for years, recently reaching level 5136, and definitely play more when Dexter's challenge is on, to the point where if it doesn't appear I generally don't bother playing at the weekend now. I really enjoy that challenge.
As so many others have previously posted I wasn't going to bother as I see others are regularly told "it's just not available for some players sometimes" and "testing" which I was willing to accept.
However, over the past two weekends, I have been receiving push notifications from the app on a Sunday telling me the space race is still on and I still have time to collect Candy for Dexter, yet when I go into the app by clicking on the notification it's still not there!
Given that I'm getting the notifications, the fact that the race isn't there MUST be a bug, surely if the developers remove it for "testing" or whatever then the notifications should be stopped as well.
To be perfectly honest, I'm getting so frustrated by it I'm seriously considering deleting the app and giving up the game altogether.
Come on King, please sort it out, it's been weeks now and loads of users are raising it as an issue...