Tried the scenario in following version :
WSO2 Identity Server 5.0.0
WSO2 API Manger 1.7.1
In this scenario WSO2 IS acts as key manager and I was following following guide
https://docs.wso2.com/display/CLUSTER420/Configuring+WSO2+Identity+Server+as+the+Key+Manager
After all the configuration is done, created an API, published it, subscribed and created an application token.
When regenerating the token I observed exact issue reported at
https://wso2.org/jira/browse/APIMANAGER-2738
[2014-09-09 11:12:04,737] ERROR - APIStoreHostObject Error in getting new accessToken
org.apache.axis2.AxisFault: Error in getting new accessToken
at org.apache.axis2.util.Utils.getInboundFaultFromMessageContext(Utils.java:531)
at org.apache.axis2.description.OutInAxisOperationClient.handleResponse(OutInAxisOperation.java:370)
at org.apache.axis2.description.OutInAxisOperationClient.send(OutInAxisOperation.java:445)
at org.apache.axis2.description.OutInAxisOperationClient.executeImpl(OutInAxisOperation.java:225)
at org.apache.axis2.client.OperationClient.execute(OperationClient.java:149)
at org.wso2.carbon.apimgt.keymgt.stub.subscriber.APIKeyMgtSubscriberServiceStub.renewAccessToken(APIKeyMgtSubscriberServiceStub.java:1187)
at org.wso2.carbon.apimgt.keymgt.client.SubscriberKeyMgtClient.regenerateApplicationAccessKey(SubscriberKeyMgtClient.java:83)
at org.wso2.carbon.apimgt.hostobjects.APIStoreHostObject.jsFunction_refreshToken(APIStoreHostObject.java:3219)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:601)
at org.mozilla.javascript.MemberBox.invoke(MemberBox.java:126)
at org.mozilla.javascript.FunctionObject.call(FunctionObject.java:386)
at org.mozilla.javascript.optimizer.OptRuntime.callN(OptRuntime.java:52)
at org.jaggeryjs.rhino.store.modules.subscription.c4._c_anonymous_3(/store/modules/subscription/key.jag:61)
at org.jaggeryjs.rhino.store.modules.subscription.c4.call(/store/modules/subscription/key.jag)
at org.mozilla.javascript.ScriptRuntime.applyOrCall(ScriptRuntime.java:2430)
at org.mozilla.javascript.BaseFunction.execIdCall(BaseFunction.java:269)
at org.mozilla.javascript.IdFunctionObject.call(IdFunctionObject.java:97)
at org.mozilla.javascript.optimizer.OptRuntime.call2(OptRuntime.java:42)
at org.jaggeryjs.rhino.store.modules.subscription.c0._c_anonymous_10(/store/modules/subscription/module.jag:35)
at org.jaggeryjs.rhino.store.modules.subscription.c0.call(/store/modules/subscription/module.jag)
at org.mozilla.javascript.optimizer.OptRuntime.callN(OptRuntime.java:52)
at org.jaggeryjs.rhino.store.site.blocks.subscription.subscription_add.ajax.c0._c_anonymous_1(/store/site/blocks/subscription/subscription-add/ajax/subscription-add.jag:206)
at org.jaggeryjs.rhino.store.site.blocks.subscription.subscription_add.ajax.c0.call(/store/site/blocks/subscription/subscription-add/ajax/subscription-add.jag)
at org.mozilla.javascript.optimizer.OptRuntime.call0(OptRuntime.java:23)
at org.jaggeryjs.rhino.store.site.blocks.subscription.subscription_add.ajax.c0._c_script_0(/store/site/blocks/subscription/subscription-add/ajax/subscription-add.jag:3)
at org.jaggeryjs.rhino.store.site.blocks.subscription.subscription_add.ajax.c0.call(/store/site/blocks/subscription/subscription-add/ajax/subscription-add.jag)
at org.mozilla.javascript.ContextFactory.doTopCall(ContextFactory.java:394)
at org.mozilla.javascript.ScriptRuntime.doTopCall(ScriptRuntime.java:3091)
at org.jaggeryjs.rhino.store.site.blocks.subscription.subscription_add.ajax.c0.call(/store/site/blocks/subscription/subscription-add/ajax/subscription-add.jag)
at org.jaggeryjs.rhino.store.site.blocks.subscription.subscription_add.ajax.c0.exec(/store/site/blocks/subscription/subscription-add/ajax/subscription-add.jag)
at org.jaggeryjs.scriptengine.engine.RhinoEngine.execScript(RhinoEngine.java:570)
at org.jaggeryjs.scriptengine.engine.RhinoEngine.exec(RhinoEngine.java:273)
at org.jaggeryjs.jaggery.core.manager.WebAppManager.execute(WebAppManager.java:432)
at org.jaggeryjs.jaggery.core.JaggeryServlet.doPost(JaggeryServlet.java:29)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:755)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:848)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:749)
at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:487)
at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:379)
at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:339)
at org.jaggeryjs.jaggery.core.JaggeryFilter.doFilter(JaggeryFilter.java:21)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
at org.wso2.carbon.tomcat.ext.valves.CompositeValve.continueInvocation(CompositeValve.java:178)
at org.wso2.carbon.tomcat.ext.valves.CarbonTomcatValve$1.invoke(CarbonTomcatValve.java:47)
at org.wso2.carbon.webapp.mgt.TenantLazyLoaderValve.invoke(TenantLazyLoaderValve.java:56)
at org.wso2.carbon.tomcat.ext.valves.TomcatValveContainer.invokeValves(TomcatValveContainer.java:47)
at org.wso2.carbon.tomcat.ext.valves.CompositeValve.invoke(CompositeValve.java:141)
at org.wso2.carbon.tomcat.ext.valves.CarbonStuckThreadDetectionValve.invoke(CarbonStuckThreadDetectionValve.java:156)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:936)
at org.wso2.carbon.tomcat.ext.valves.CarbonContextCreatorValve.invoke(CarbonContextCreatorValve.java:52)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1004)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1653)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:722)
[2014-09-09 11:12:04,749] ERROR - subscription-add:jag org.wso2.carbon.apimgt.api.APIManagementException: Error in getting new accessToken
The solution is I've missed following point in the guide...
Copy the section from the identity.xml file in the API Manager (/repository/conf/identity.xml) and replace the section of the identity.xml file of the IS (/repository/conf/identity.xml).
Thought of sharing this hoping that someone will come across the same issue :)