I am having this problem as well. I reset the hub and now can log into my devices (camera and light) via the web browser but the app reports "Session Error. We've encountered an error. Please try again. [Error. #43504]"
This just started happening in the last 48 hours. I deleted the app and reinstalled it on my iPhone 6+ without any success.
Hi MEdwardswa -
It looks like you signed up with Xfinity Home under a non-Comcast email domain. You cannot use the mobile app unless you login with a Comcast email. I have already opened up a ticket with Customer Support to help you get this resolved.