Hi,
I'm not sure whether you created the node by providing values for all mandatory or required properties. I've provided below the list of properties (sample) which I use to create a node and the polling happens. Try it and let us know if any issues. Also please check if the correct poller is assigned to the node.
"EntityType":"Orion.Nodes",
"IPAddress":"10.10.1.1", Sample
"IPAddressGUID":"044648a4-0000-0000-0000-000000000000", Sample
"Caption":"",
"DynamicIP":"false",
"EngineID":"1",
"Status":"1",
"UnManaged":"false",
"Allow64BitCounters":"false",
"SysObjectID":"",
"MachineType":"",
"VendorIcon":"",
"ObjectSubType":"SNMP",
"SNMPVersion":"2",
"Community":"public",
"RediscoveryInterval":"5",
"PollInterval":"120",
"StatCollection":"10",
"BufferNoMemThisHour":"-2",
"BufferNoMemToday":"-2",
"BufferSmMissThisHour":"-2",
"BufferSmMissToday":"-2",
"BufferMdMissThisHour":"-2",
"BufferMdMissToday":"-2",
"BufferBgMissThisHour":"-2",
"BufferBgMissToday":"-2",
"BufferLgMissThisHour":"-2",
"BufferLgMissToday":"-2",
"BufferHgMissThisHour":"-2",
"BufferHgMissToday":"-2"
Also for adding created Nodes to NCM, there is a Verb "AddNodeToNCM" which accepts the NodeID as parameter. The sample script has example on how to invoke verbs. Try this and let us know.