Facebook not loading on iPhone

First try a forced restart, if that doesn't work reinstall the app. If that doesn't work contact the app developer for help with their software.

Try a forced restart.

• Press and quickly release the volume up button

• Press and quickly release the volume down button

• Press and hold the side button.

• When the Apple logo appears, release the button.

Force restart iPhone - Apple Support (IN)

Here is a link to Facebook's help page -

https://facebook.com/help

Delete the app and redownload from the App Store