You cannot directly add SolarWinds NCM servers that are running version 6.1 or earlier to SolarWinds EOC. Instead, you install and configure the SolarWinds NCM integration module on a SolarWinds Server and then add that server to SolarWinds EOC.
If you want to add your SolarWinds NCM server to SolarWinds EOC directly, upgrade NCM to version 7.0 or higher.
You must have correctly configured the SolarWinds NCM Integration module with a valid SolarWinds NCM server and a valid SolarWinds NCM credential.
The SolarWinds NPM credential you specify in SolarWinds EOC must not have any account limitations that would prevent access to the SolarWinds NCM integration module.