There is a button on the toolbar that toggles word attributes on and off. Word attributes are Strong's numbers, Goodrick-Kohlenberger numbers, Greek parsing tags, or any other information that might be attached to the words in a Bible. It is easy to toggle word attributes off without realizing it if you happen to be looking at a Bible that does not have word attributes when you do it.
The toolbar button looks like a Greek alpha and Hebrew alef character. On an iPhone, it might be on the extended area of the toolbar that is to the right of the portion you normally see on the screen. Swipe right-to-left over the toolbar to reveal these additional toolbar buttons. Tap the button to toggle word attributes back on. You'll see a brief message at the bottom of the screen to confirm that you've turned word attributes on (or off).