Alexa and openHab with MAX! thermostat, device is currently not responding

I have openHAB 2.4 with the Alexa skill. If I ask Alexa for the temperature or want to set the temperature for the thermostat item (gBedroom_Thermostat) I get the answer (<Gerät> reagiert gerade nicht) device is not currently responding. But I can ask the temperature for my item “Bedroom_Temperature”. If Alexa looks for new items it can only find the [“Thermostat”] and the [“CurrentTemperature”] item. The [“TargetTemperature”] is not listed. Only the item [“CurrentTemperature”] is responding/working well.

Group     gBedroom_Thermostat              "Schlafzimmer Thermostat" (Bedroom, gThermostat)      ["Thermostat"]
Number    Bedroom_Temperature             "[%.1f °C]"            <temperature>   (Bedroom, gTemperature, gBedroom_Thermostat)       {channel="homematic:HG-BC-RT-TRX-CyG-2:7e0bd100:LEQ1256338:1#ACTUAL_TEMPERATURE"}
Number    Bedroom_Temperature_Label1      "Schlafzimmer Temperatur" ["CurrentTemperature"]                      {channel="homematic:HG-BC-RT-TRX-CyG-2:7e0bd100:LEQ1256338:1#ACTUAL_TEMPERATURE"}
Number    Bedroom_Heating                 "[%.1f °C]"            <heating>       (Bedroom, gHeating, gBedroom_Thermostat)           {channel="homematic:HG-BC-RT-TRX-CyG-2:7e0bd100:LEQ1256338:1#SET_TEMPERATURE"}

Is there any logging I can view (I didn’t see anything either in openhab.log or events.log)?
What is my mistake that I cannot work with thermostat item and Alexa?

Now resolved:
My mistake was that I have not set the group gThermostat for the item configured with [“CurrentTemperature”] and [“TargetTemperature”]:
The result is

Group     gBedroom_Thermostat             "Schlafzimmer Thermostat"          (Bedroom)  ["Thermostat"]
Number    Bedroom_Temperature             "Ist-Temparatur [%.1f °C]"         <temperature>  (Bedroom, gTemperature, gBedroom_Thermostat) ["CurrentTemperature"]         {channel="homematic:HG-BC-RT-TRX-CyG-2:7e0bd100:LEQ1256338:1#ACTUAL_TEMPERATURE"}
Number    Bedroom_Heating                 "Soll-Temparatur [%.1f °C]"        <heating>      (Bedroom, gHeating, gBedroom_Thermostat)     ["TargetTemperature"]          {channel="homematic:HG-BC-RT-TRX-CyG-2:7e0bd100:LEQ1256338:1#SET_TEMPERATURE"}