Mobile app and router

At my house I can not get the mobile app (Android version) to work correctly. It show the list of riders only and not the action items or ride data. And yes, both the app and PC are on the same WIFI access point. As a test, I tried my configuration with same computer and android phone on my friends house and it worked fine. So I suspect it has to do with some peculiarity of my home network. The cable modem / router box is the ARRIS TG862 that many comcast customers have. No other routers / access points in the house.
Any Comcast customers out there have success getting the app to work ?
Any tips on how the app inter-operates with Zwift application ? I’d like to use some network diagnostics to try and figure out what is happening.