Setting up a trial - HP Procurve 5400zl switches are outputting sFlow on port 9996 but no devices showing

Setting up a trial - HP Procurve 5400zl switches are outputting sFlow on port 9996 but no devices showing

Any idea what I am missing, trying to trial the netflow analyser - the switches are now set to output sFlow data on port 9996, there is nothing I can see that is blocking any traffic but no devices are appearing in the dashboard.  What do I try next?
 
Thanks in advance for any help you can offer.
 
Alistair

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