Firstly, please accept our apologies for this inconvenience. We suggest that you make sure that the app on your device is up-to-date. If it is, uninstalling and downloading the app again should fix the issue. We have a small guide on how to do so in our Can I play in the mobile browser, or do I need to download an app? article.
If the above does not work, please take a screenshot of any errors you may find to be able to send to our Customer Support.