Connected device not showing

An iPhone7 is connected to my Gateway router, but it doesn’t appear in either the mobile app or the myxfi on the computer. It does appear when I log directly into the router at 10.0.0.1. Have updated firmware, reset to factory default and then updated firmware, rest phone network settings and restarted phone and forgot network and rejoined. A dozen other devices all appear as expected except this one iPhone—so I can’t apply parental controls to a device that doesn’t appear