Cannot Download

I keep getting emails from Xfinity saying that I can find out such things as my WiFi data usage, advanced security, etc.  But when I attempt to see how my wifi service is performing, I am told to download an app to my smartphone.  When I try to download the app, I am unable to.  It tells me that my OS is too old and to update it.  But when I check my update settings on the phone, it says I have the latest OS.  I have a Samsung Galaxy Note 8.