We are currently experiencing sign in problems for some users with iOS 7 using our iOS app. This is because Apple has changed something in the cookie handling in iOS 7. To solve the problem you need to update the cookie settings in Safari:
Go to the Settings app -> Safari
Change “Block Cookies” to “Never” or “From third parties and advertisers”.
Kill the SpamDrain app or restart your phone and try to sign in again.

We apologize the inconvenience and we are working to fix this as soon as possible. But it take a week or so before a new version is approved in App Store.