First, it may be a network problem. Poor network signal may cause players to log in, so players need to switch to other networks with better signal.

Second, it may be the problem of mobile phone cache. Players need to clean up the cache of their mobile phones properly.

Third, it may be the problem of mobile phone antivirus software. Players need to set permissions in security settings or turn off antivirus software directly.

Fourth, it may be the server. The server is under maintenance or there are too many players, which will make it impossible to log in. Players need to wait for official repair or notification.

Fifth, it may be the version of the game. Players need to download and install the latest version of the game in official website.