I'm having the same issue. My son is sitting right next to me and is watching YouTube on his tablet. It's not showing up on the app as connected. Neither is my wife's phone. They have before. Obviously, my son is now bypassing the time restriction. And yes, I have rebooted gateway and logged out of app, and did everyother of the usual generic recommendations.
Check to see if you can find the device in the gateway's list of connected devices.