Hello Phani,
Thank you for your reply.
Yes I can see the device on the USM when adding its profile from the SNMP collector.
And yes the discovery agent is installed in the same server with the snmp collector. and we discovered other devices.
And regarding the device, it accepts the SNMP v2c and v3 perfectly when using 3rd party tool from the snmp collector server.
So I think the problem is only when discovering from USM.