In a network apparatus for receiving a processing request transmitted from an external apparatus connected thereto via a network, it is detected that processing corresponding to the transmitted processing request has not been performed. If it is detected that the processing corresponding to the transmitted processing request has not been performed, a port number of a request destination of the transmitted processing request is recognized and an application corresponding to the recognized port number is specified as an application of a request destination of the transmitted processing request. Furthermore, it is determined whether the specified application is in an ON or OFF state. If it is detected that the processing corresponding to the transmitted processing request has not been performed and the specified application is in the OFF state, error information including information indicating the specified application is output.