Hi @hatgirl!

Thanks for bringing this up. The quickest way to check that it's installed is to go to your Home screen then swipe left and type Square into the search bar. Best case scenario is that it might be hiding in a different folder.

If there are no results, it's safe to say that it didn't properly install. In that case, it may be that your phone isn't able to handle the updated version of the Square app since it is an older model. I would reach out to Apple to see if there is anything you can do from there.