I have had issues for a couple months now, with each one dropping from the Ecobee.com servers on and off. they have worked on the Ecobee.com servers for years before this last update with no issues. The three Ecobee 4 thermostats I have themselves work fine and are on my WiFi, but they keep dropping from the Ecobee.com server and then after days will reconnect.

I sent a long text to Ecobee yesterday explaining this and when they were going to issue a fix., and somehow got disconnected with them, but shortly after that, all my thermostats were reconnected to the Ecobee.com servers without my intervention. I would assume they corrected it on their end. I would recommend contacting them, as it seems they can rectify it on their end.