Ticarium is an online game, make sure your device is connected to the internet. If your device is connected to the internet, you can try reopening the game by closing it from the background.
Also, ensure that your game is up to date. If your game isn't up to date, you will receive a warning, but if a critical error has occurred without a warning, we have probably fixed it and released an update.
How can I check for game updates? 

If you are still experiencing issues or encountering access problems, you can contact us by clicking the support button within the game and sending us a screenshot or screen recording.