Simple snmp-plugin is not working yet

I think your

detect = startswith(".1.3.6.1.2.1.1.1.0", "RZ-Products GmbH, DCM Agent"), # sysDescr

dosent match. You can try cmk -vvII <hostname> to see what cmk really finds.

Then there is a second issue. In your register.check_plugin you define a service with item (service_name = "Temperatur %s",), but in your function discover_temp you do no return an item name. You sould change this to

yield Service(item="your item name")

And one more.

yield Result(State.OK, summary="OK")

is missing the state= parameter.

yield Result(state=State.OK, summary="OK")