My teenager has started missing prayers, especially Subuh, because he stays up late on his phone. What should I do?

Start with the cause, not a lecture: the late-night phone that robs him of sleep and his Subuh. Staying up late makes teenagers too tired to wake up, and prayers are missed one after another. Agree together on a time to put the phone away at night, and keep its charger outside the bedroom as a start. Make Subuh a family affair: wake him gently and wait for him with a simple breakfast, not with scolding. Allah says: “Enjoin prayer on thy people, and be constant therein” (Surah Taha 20:132) — that constancy includes accepting that change comes gradually. Praise every Subuh he makes, because encouragement strengthens a habit better than guilt. See digital & family.