UPDATE, MAY 17, 2016: Sounds like Apple is finally fixing the Game Center issue with an update to iOS 9.3.2 (read about it here), however ALWAYS, ALWAYS back up your device before updating the OS.
We have heard that Game Center has been experiencing technical difficulties and believe this could be affecting Race The Sun (as well as other games that integrate with Game Center). As a result, we have been looking for ways to resolve Game Center issues and found an idea. Below is a set of instructions you can try to follow in order to hard restart your device and successfully log into Game Center.
close all running apps
go into airplane mode
force restart your device by pressing the Sleep/Wake (on/off) button and Home button simultaneously until you see the Apple logo
go to Settings > Game Center and log out of Game Center
disable airplane mode and enable wifi
- log back into Game Center from Settings > Game Center
If this works for you, please let us know. If it does not work for you, please also let us know. This is our best idea so far and any new information you can give us will help us resolve any related problems experienced with Race The Sun. Thank you for your patience and for helping us trouble shoot this issue. We greatly appreciate your help.
And yes, we are working on an update to prevent this problem from occurring.