Screen shot not working

If you're using the correct steps to take a screenshot and if you were able to do it before the latest update, that's the first time I read about that.

What happens when you try? Are volume up and right side (power) buttons working normally when you use them separately?

Should be this case, have you already tried to install a fresh copy of iOS on your XR, using this procedure?:--> Restore your iPhone, iPad, or iPod to factory settings – Apple Support

Regards

Giulio

Try restarting the iPhone and try again. Make sure you are following the steps here for a screenshot, Take a screenshot on your iPhone - Apple Support