Our team is aware of the issue! We're doing our best to resolve it as soon as possible. For now, we recommend doing the following:

iOS 13 users - log out of the Game Center, and load the game.
Android users - log into your Google Play account and load the game.

In case of any further issues, don't hesitate to contact us via nitro-support@creative-mobile.com! We'll do our best to help!