Depending on your version and configuration of AIX, the file that controls snmp differs. Check whether /usr/sbin/snmpd is linked to /usr/sbin/snmpdv3ne:
If it is linked to snmpdv3ne or snmpdv3e, then the relevant config file is /etc/snmpdv3.conf, not /etc/snmpd.conf. (The active snmp agent is controlled by snmpv3_ssw. snmpv3_ssw -n will switch to the non-encrypted, v3 agent.)
To allow AIX monitoring, you just need to ensure that the config file (snmpd.conf or /etc/snmpdv3.conf) allows the LogicMontor collector to query the system. Ensure that the collector has access with the community you expect, and that all views are included. Ensure that any line such as:
AIX Monitoring with the net-snmp agent
The native AIX snmp daemon is not easily extended, and doesn't report some things as well as the net-snmp agent. However, the net-snmp agent cannot report some things about AIX systems. Thus if you want to run the net-snmp snmpd, we recommend you configure the AIX agent to receive some requests proxied from the net-snmp version of snmpd.
If you still cannot add your host, you may want to try adding just a single proxy configuration line, instead:
proxy -v 1 -c public 127.0.0.1:1610