CRIT - no unmonitored services found, no vanished services found, no new host labels, [agent] Communication failed: [Errno 111] Connection refused

Thanks! i am sorry for this delay i was out of office this days.

AFTER so MUCH personal effort i finally took the answers needed. Please update setup tutorial of the installation to include this topic.

This is an agentless - snmp v1 - query of a host.

Step 1:
There is nothing to do about server setup the only thing you have to do is to disable this rule → Setup - Services - Catalog of check plugins - Applications - Checkmk - Checkmk: Discovery Procedure, which is bound to execute each time you create a new host. This rule generates errors if you dont disable it.

Step 2:
Enable SNMP Service in Windows Clients. This is a tutorial that helped me: https://theitbros.com/snmp-service-on-windows-10/. Don’t forget to add a community name public with READ ONLY permissions.