Why can’t I use texting? The app opens and then closes right away.

Try uninstalling and then reinstalling the app.

Close the app completely if you can then reopen and test. I believe you view your open apps and then swipe up to close it.

Then try to power the phone off all the way by shutting it down. Quite a few issues with phones can be fixed by simply cycling the power. Test after powering back on.

You can then try clearing the app data or cache in the system settings. Test the app again.

If that doesn’t work, try to uninstall the app and reinstall if possible. Then test once more.

If all else fails here, then you may want to do additional research but the last resort would be a factory reset and restore the device to factory defaults.