Please try the following:
1. Clear all background apps to ensure that the phone has enough memory.
2. Restart the phone and then reopen the app.
3. Go to Settings> Apps> See all Apps> Find the App> Storage & Cache> Clear Storage and Clear Cache.
4. Check if your phone and the application have the latest system or version. If not, upgrade them to the latest.
If the issue persists, contact the Nothing Support Team for further assistance.