Please tell us some basic information before asking for help:
How to fix this
Try clearing camera app data and cache and restart your phone once
Hi, we'd request you follow the below steps:
1. Check your phone for the latest software version.
2. Go to Camera settings.
3. Clear cache & storage of Camera App after backing up & disable/re-enable camera App
4. Try the same under safe mode:
Hold the power button for 5 seconds => When the screen flashes with option => Press & hold power option => You will get an option to restart in safe mode
5. If still you face the issue factory reset your phone after taking a full backup: https://www.asus.com/support/FAQ/1006346/