Are you connected to your gateway's SSID with that device?
Can you try clearing App Cache and Data from your device?
To do so, first open the Settings menu, then tap Apps & Notifications. Tap on the Xfinity Home app, then tap the Force Stop button. When the app is closed, tap Storage then Clear Cache. Then try opening the app again. If the issue persists, you may need to repeat these steps.
Adam856 -- Wanted to check in again with you. We released an updated version of the app which we think may also help.