I can’t check for update on my iPhone x

As Kurtosis12 suggested, you can disable low power mode and connect to WiFi. If this does not work, you can try restarting your phone. You can also update your phone with your computer (https://support.apple.com/en-us/HT204204). If none of this helps, you can try this article: https://support.apple.com/en-us/HT201435.

Connect to WiFi (not a hotspot), turn off low power mode and make sure your battery is at least 50% charged or better yet, connect to a charger