Hi @Kendalljo, open the T-Mobile Internet app. Click on the “Devices” tab at the bottom.  All your connected devices will be shown.  Some will have their actual name.  Others will only show the last four digits of their MAC address. By clicking on the devices listed more information will be displayed for each device.

Every time I click that, for the last 2 weeks, it says Gateway has not responded and may need to be restarted. I restart it try again, and it tells me AGAIN gateway is not responding and may need to be rebooted. 

ANNOYED

Same here. Agreed. It is frustrating. There is an app called Fing that is able to see the devices connected. 

Thanks for the door opener!!

Similar free app for Mac computers “IP Scanner” app -- in the App Store.

But still -- there is **NO** excuse for T-Mobile long time (years, according to Community) failure of their app to do this reliably.