You're not the only one having this problem! When I access the app I am seeing the message "communication with the system has been lost". I've deleted the app from my phone and reset the Internet connection on the evohome ( wifi model) with no joy.
Interestingly I have received no email saying connection has been lost. In the terms and conditions section of the app it says I need to agree to new terms to continue he using the service but there is no way of doing so. So I thought therefore it might be an idea to log in to Total Connect Comfort via the web to see if I could do so there. Problem is I can't log in there, it just hangs.
I've tweeted Honeywell to see if they are having any problems at there end, but seeing as you have also posted I am thinking that maybe they are.
Just for clarity I am uk based, and I get the feeling that my system probably went down around 04.30 our time as the app is stating a target temp of 5 degrees for the hall, which ties in with the time our front door was opened as my son left for work, thereby activating the open window function.