Metadata not avaailable in Cognos 10.2.1

I am using AIX platform with Cognos 10.2.1 version and it is not distributed environment.
The report is running perfectly since last week but suddenly showing below error

DPR-ERR-2056 The Report Server is not responding.</messageString></message></messages>    http://www.ibm.com/xmlns/prod/cognos/reportService/201301/.absoluteHandler trace back: [the_dispatcher] com.cognos.pogo.handlers.performance.PerformanceIndicationHandler [the_dispatcher] com.cognos.pogo.handlers.logic.ChainHandler [service_lookup] com.cognos.pogo.handlers.engine.ServiceLookupHandler [load_balancer] com.cognos.pogo.handlers.logic.ChainHandler [lb_forwarder] com.cognos.p2plb.clerver.LoadBalanceHandler [reportservicechain] com.cognos.pogo.handlers.logic.ChainHandler [warp_with_authenticate] com.cognos.pogo.handlers.logic.ChainHandler [do_warp] com.cognos.pogo.handlers.logic.ChainHandler [warpmta] com.cognos.pogo.reportservice.ReportServerHandler

I tried to open the report in Report studio, threw same error .
FYI, I executed other report it ran successfully.

It is very strange error.

Please help out from issues asap.
Many thanks in advance for quick solution.

BR,
Kumar