The yellow LED staying on means that there is a WiFi communication problem between the radiator and the home internet: if the WiFi connection is weak or slow in the room where the radiator is installed, then we recommend installing a booster.
In the app, this means that there will be two lines on the room tab associated to the radiator in place of the temperature reading: therefore, even when correctly associated, or if there is no WiFi connection, the radiator will not be able to communicate the temperature reading from the app and may not respond to the changes made in the app itself.
The electric radiator may in any case operate in manual mode.