An E05 error on the Smart AC Control indicates an issue with the internet connection. The hostname could not resolve to the Internet Protocol (IP) address using the Domain Name System (DNS).
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.
Go to the DNS settings in your router, and
set Google DNS as your primary DNS. To do this, set the address of the DNS server to 126.96.36.199 and the address of the alternative DNS server to 188.8.131.52.
If Google DNS is not available in your country, change the DNS server to a different one used.
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.