Same again here.
It's a real pain when you have two accounts in an Amazon Household. As I understand the configuration at the moment I have to drop the skill and re-attach it to both accounts. To date I have not lost any device names or groups, seems these are stored else where. I discovered this as I have been building some devices to interface directly to my Echo devices via the UPnP protocol with various names and groupings. These seem to behave the same way as the Honeywell Total Connect Comfort device names / groups. hence probably why they are not being lost. As I have 12 additional name / groups I am rather relieved not to have to recreate them.
Drop the skill and reconnect seems to fix the issue. Wonder if I can have Alexa do this for me!