During a firmware upgrade, the Daikin LAN adapter stops the communication with your Daikin user interface. As a side effect, an error code is shown on your Daikin user interface. When the adapter is fully upgraded, the communication will restart and the error will disappear from your user interface.
It’s expected to see temporary the error code “U8-01” on your Daikin Altherma User interface
It’s expected to see temporary the error code “U4-66” on your Daikin Boiler.