What do the error codes Er0, Er1, Er2, and Er3 mean on the Bliss Wifi Chrono Thermostat?

Er0 indicates a Generic Error, Er1 indicates an Internet Failure (caused by ADSL being off, Wi-Fi too distant, congested traffic, or incorrect SSID/password), Er2 means a data connection was made but Bliss did not receive an answer (unstable or congested data traffic or cloud communication problems), and Er3 means data received was corrupted due to a connection failure during cloud communication or a very disturbed line. You can attempt a force sync by long-pressing the Finder logo while the display is off until the horizontally-moving dashes appear. (Page 18)