Unable to invoke RPC on NE using mountInstance.getRpcService()

When I try to invoke RPC on NE using the rpcservice object returned by mountInstance.getRpcService I get the following exception -

Caused by: java.lang.IllegalStateException: No default provider is available
at org.opendaylight.yang.gen.v1.urn.cisco.params.xml.ns.yang.ldna.rev131024.LocalDnaService$$Broker$DirectProxy.dnaTaskRefresh(LocalDnaService$$Broker$DirectProxy.java)
at org.opendaylight.controller.dna.DnaService.dnaTaskRefresh(DnaService.java:116)
at org.opendaylight.yang.gen.v1.urn.cisco.params.xml.ns.yang.dna.rev131024.NetworkDnaService$$Broker$DirectProxy.dnaTaskRefresh(NetworkDnaService$$Broker$DirectProxy.java)
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