HP Procurve is in the process of rebranding some of their enterprise switches to Aruba. I'm not sure if that is reason this is happening but we recently purchased two 5400R ZL2 switches and found that the health of power supplies and fans is not natively supported by NPE although every other of the dozens of HP Procurve enterprise switches that we have our system are.
I opened a case on this and the tech recommended that I post a feature request. The case is: Case # 1085809 - Hardware Health issue