It's finally here!
Dark theme has been rolling out and is now available to all on Android. Toggle it on/off in Settings → https://goo.gl/YNrzyT
Note: you'll need app version 13.37 to see the feature.pic.twitter.com/kmX1dwZCjp
We'd like to help. Does this issue happen across devices? Try checking if there are any pending updates for the app, it generally fixes most of the issues. Let us know if that does the trick.