See in configuration->Tools if every extruder has set "Extruder Managing Temperarures" to the own extruder number.
If this is the case, go to console and enable ack and disable M105 filter and see what firmware says. Some do only report temperature for active printer. Correct answer will contain T0: and T1: in temperature report - if only one temperature is reportet as T: and we get no infos for other extruders to show.
