Based on what the manual says, @ulist is correct.
If your fridge didn't have >20°C then the temperature sensor may be defective. This is a well-known problem, unfortunately. Try search for "Temperaturfühler Kühlschrank" in this forum and in nuggetforum.de.
Gruß, Stefan
Columbus 600D, MJ150 (2013), Winterpaket, 100Ah LFP, 200WP Solar, VBCS, 1500W Sinus WR, Grabber 235/75R15, 8" ZLF, Lesjöfors