An error occurred during setup of Reporting extensions.
Reason: Invalid URL: The URL is empty.
Le problème survient lorsque la valeur UrlRoot ou UrlString , selon la version de SSRS installé, n’est pas configurée correctement dans le fichier rsreportserver.config. Voici l’extrait de la documentation Ax Installation
Update the Reporting Services 2005 configuration file
If you are using Reporting Services 2005, use the following procedure to update the configuration file.
Open the rsreportserver.config file. By default, this file is located in \Program Files\Microsoft SQL Server\ReportingServicesInstance\Reporting Services\ReportServer.
Locate the UrlRoot XML element and update the URL in that element, if necessary. For example, if you implemented SSL, you may need to change http to https, as shown: <UrlRoot>https://ServerName:PortNumber/reportserver</UrlRoot>
Save your changes and close the file.
Update the Reporting Services 2008 configuration file
If you are using Reporting Services 2008, use the following procedure to update the configuration file.
Open the rsreportserver.config file. By default, this file is located in \Program Files\Microsoft SQL Server\ReportingServicesInstance\Reporting Services\ReportServer.
Locate the UrlString XML elements and update the URL in each of those elements, if necessary. (There are two UrlString elements.) For example, if you configured the virtual directories to use port 81, you may need to change the port number, as shown: <UrlString>http://+:81</UrlString>
Save your changes and close the file.