After updating the aqua server, users can still work with old aqua client until they close it. When restarting the aqua client, the user receives an error message and a download URL for the new aqua version. You can configure this Download-URL in web.config file located on the server path
C:\Program Files\andagon GmbH\aqua For IIS\Web
Here you can set ClientDownloadUrl in order to show a proper URL for downloading the new aqua.msi installer.