Error Code TVAPP-00100

I have a 55" Insignia Roku TV, on which I'm receiving the TVAPP-00100 message every time I try to use the Xfinity Stream app.  I have tried the 'unplug the modem' solution and it had no effect for me.  The app works fine on my 42" Insignia TV, tablet, and cell phone.  Only the 55" doesn't work.  I have also tried uninstalling and reinstalling the app, to no avail.  Please help!