Thanks for reaching out. Our engineering team is already looking into this issue. We ask that users post to our XFINITY forums as it allows us to pull up your account details and share them with our engineering team to troubleshoot. I will reach out when I have more information!
I am having the same issues. The Infinity Home App will NOT connect via Wifi but will connect immediately if I turn off Wifi and it only has a cellular connection. Every now and then it will connect via Wifi but I must force close the app and then re-open to get a update. I have uninstalled and re-installed numerous times and am running iOS 11.2.1 on a iPhone 6.