KM200 "com.google.gson.JsonObject.get(String)" is null

Add-ons Bindings
1

Hi everybody,

I am struggeling with my KM200 thing.

I have

  • set up openhab 5.2.1 with the KM200 binding
  • cleared the cache with openhab-cli
  • removed all things
  • removed the binding
  • reinstalled the binding
  • autodiscovered my heating and added the new thing
  • reset my internet password
  • generated the private key at https://km200.andreashahn.info/

The thing starts beyond the “cannot communicate“.
DEBUG – org.openhab.binding.km200.internal.handler.KM200GatewayHandler – Test of the communication to the gateway was successful..

However it looks like there is a comunication problem which I cannot attribute

Log Details
Time
14:51:31.359
Timestamp
Feb 21, 2026, 2:51:31 PM
Level
ERROR
Logger Class
org.openhab.core.internal.common.AbstractInvocationHandler
Message
An error occurred while calling method 'ThingHandler.initialize()' on 'org.openhab.binding.km200.internal.handler.KM200GatewayHandler@d2df0fd': Cannot invoke "com.google.gson.JsonElement.getAsString()" because the return value of "com.google.gson.JsonObject.get(String)" is null
Stack Trace
java.lang.NullPointerException: Cannot invoke "com.google.gson.JsonElement.getAsString()" because the return value of "com.google.gson.JsonObject.get(String)" is null
at org.openhab.binding.km200.internal.handler.KM200GatewayHandler.checkConfiguration(KM200GatewayHandler.java:259)
at org.openhab.binding.km200.internal.handler.KM200GatewayHandler.initialize(KM200GatewayHandler.java:129)
at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
at java.base/java.lang.reflect.Method.invoke(Method.java:580)
at org.openhab.core.internal.common.AbstractInvocationHandler.invokeDirect(AbstractInvocationHandler.java:149)
at org.openhab.core.internal.common.Invocation.call(Invocation.java:52)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:317)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)
at java.base/java.lang.Thread.run(Thread.java:1583)