Switch Port & IP Address Management Software
Community refers to the SNMP Community string of the device. For most of the devices, the default community string is "public".
You can use the SNMP Tools - -> Community Checker tool to get the community string of the device. It has a list of default community strings of various devices, which queries to find the matching community string of the device.
Please ensure that the queried device is SNMP enabled.
To install or enable SNMP in Windows or Linux OS, refer to the online help documentation
The possible reasons could be: