An E04 error on the Smart AC Control indicates that the connection to our tado° servers failed.
To fix this, please do the following:
Make sure that your Wi-Fi is activated and working. To do so, check Wi-Fi access on other devices or the LEDs on the front of your router.
If needed, reset your Wi-Fi network.
Then, give the Smart AC Control a few minutes to connect to the Internet.
Please note: when the internet connection is temporarily lost, you can control your AC via the user interface on the Smart AC Control. You can also use your old AC remote for this.
More information: