This behavior may happen on some devices after an App update.
Not to worry, there is a solution :
1) Leave the app running in the background
2) Go to your Android System Settings > App Settings > Cirus
3) in "Storage" select "Clear Data", then select "Clear cache"
4) Reopen the app from your homescreen
5) You should see a cool intro animation, and you'll be asked to log in again
6) Enjoy Cirus!