Check the other 5 servers for how they are polling for memory - I've seen a few Linux servers running old versions of net-snmp before where the agent doesn't support the required MIBs.
Check List Resources - Are the stats definitely pulled from "CPU & Memory", or are they pulled back as volumes? If they're being pulled back as volumes, you'd need a separate report for thoe 5 servers as its a different object type.
One thing to check is if you have any NULLs under the Location field as this can cause issues.
Also having the fieldname with space or special characters might cause an issue like this.
Problem fixed. For some reason the snmpd.conf file went to default value. I modified it with our public ro community string and now all seven servers are appearing on Report.
What confused me was the servers were up and reporting on Orion NPM screen. I did not suspect the SNMP configuration due to this.
We can close this thread.