Unclear subscription problem - by: yp

Hi,
I'm evaluating the QuickOPCUA .NET solution but I'm struggling with the subscription part. I've created a subscription like this:
//Node 'A.B.C" has value string
nodeid = new UANodeId(2, "A.B.C");
easyUAClient.SubscribeDataChange(host, nodeid, 0, OnValueChanged);

The 'OnValuechanged' routine isn't called at all when the value on the OPCUA server gets changed as a result of either internal value changes, or when I modify it from another OPCUA client. It does get called when I call it form the same process when I do an explicit write (easyUAClient.WriteValue(host, nodeid,"yp says hi");
Also my other external OPCUA client reflects the changes of my easyUAClient write so I conclude that the type and the nodeid are correct.
Any hints on what could be the isssue?
Regards.