Thanks a lot for the quick reply. Did all of that before.
I managed to find the problem, I had to install the Pi4J library.
sudo apt-get install pi4j
&
Now the MC23017 Things are online, but a new error appeared:
2019-12-17 20:43:55.624 [ERROR] [nal.common.AbstractInvocationHandler] - An error occurred while calling method 'ThingHandler.handleCommand()' on 'org.openhab.binding.mcp23017.internal.handler.Mcp23017Handler@107c4f9': null
java.lang.NullPointerException: null
at org.openhab.binding.mcp23017.internal.handler.Mcp23017Handler.handleOutputCommand(Mcp23017Handler.java:116) ~[?:?]
at org.openhab.binding.mcp23017.internal.handler.Mcp23017Handler.handleCommand(Mcp23017Handler.java:83) ~[?:?]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_222]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_222]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_222]
at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_222]
at org.eclipse.smarthome.core.internal.common.AbstractInvocationHandler.invokeDirect(AbstractInvocationHandler.java:152) [bundleFile:?]
at org.eclipse.smarthome.core.internal.common.InvocationHandlerSync.invoke(InvocationHandlerSync.java:59) [bundleFile:?]
at com.sun.proxy.$Proxy190.handleCommand(Unknown Source) [?:?]
at org.eclipse.smarthome.core.thing.internal.profiles.ProfileCallbackImpl.handleCommand(ProfileCallbackImpl.java:74) [bundleFile:?]
at org.eclipse.smarthome.core.thing.internal.profiles.SystemDefaultProfile.onCommandFromItem(SystemDefaultProfile.java:48) [bundleFile:?]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_222]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_222]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_222]
at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_222]
at org.eclipse.smarthome.core.internal.common.AbstractInvocationHandler.invokeDirect(AbstractInvocationHandler.java:152) [bundleFile:?]
at org.eclipse.smarthome.core.internal.common.Invocation.call(Invocation.java:52) [bundleFile:?]
at java.util.concurrent.FutureTask.run(FutureTask.java:266) [?:1.8.0_222]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [?:1.8.0_222]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [?:1.8.0_222]
at java.lang.Thread.run(Thread.java:748) [?:1.8.0_222]```