Hi Pavan,
Try to Put error Handling for the rest call and print the stack trace. This will give a clear idea of what the error is about.
Hi Pavan,
Right click the call REST -set as error handling-select custom with rollback. Below the call REST add a log message activity, inside that set as error in log level, give the node name ,in template set as{1} in parameters add latesterror/message. After connecting the path(->) to log message right click the path and select -set as error handler. Try to debug you will be able to see the error in call REST .