The machine on which ArcGIS Monitor Server is installed must have an authorization file. There are several ways to register ArcGIS Monitor Server. You can visit My Esri to obtain an authorization file before proceeding with the installation. You can also register Monitor Server using the Software Authorization Wizard after the software installation is complete (this is the recommended method).
Registration numbers similar in format to ABC123456789 are required. Visit My Esri for more information.