If Legacy Authentication Methods uses AD FS authentication, the application configuration file of the Legacy Authentication Methods client (ReportServices.exe.config) must be updated to enable AD FS.
CAUTION:
If this is a ClickOnce deployment, any changes to the files in the deployment folder or the contents of the deployment folder, such as custom changes to the ReportServices.exe.config file, must be made before clicking Next at the Deployment Signing dialog box.
To enable AD FS authentication for the Legacy Authentication Methods client: