During server maintanence, you cannot run the PUBG Mobile application.
You can check the maintanence schedules on our official community.

If the game doesn't run even when there's no server maintanence, please follow the steps below.

[Steps to resolve application running issues]
1) Delete all unnecessary application and data from your mobile device
2) Check your OS verison and update to latest version if possible
3) Check your network(Wi-Fi/data) connection
4) Reboot mobile device

※ If the problem persists, please remove PUBG Mobile completely from your mobile device and try installing it again when you're connected to a strong Wi-fi/data network.
(Please note that your guest account information will be lost once you remove the game from your mobile device.)

※ If the issue persists after following all steps above, please contact PUBG Mobile Support along with the model name of your mobile device and the OS version.