What app is missing -- Alexa or iOS version?
Your hubby needs to get in step and get with the program. Too many apps depend upon a recent or current iOS being installed. My iPhone has v10.3.3 installed and so does my new iPad. In fact, I upgraded to a new one recently because my five year old iPad has not been upgraded past v9 for over a year. After a few years, even Apple stops upgrading iOS on an old gadget. If your hubby's phone cannot go above a certain version, then he needs a new phone. Such is life with smartphones, tablets and computers.