Error on system configuration wizard: "Can't get instances of the server class"
This error typically appears after upgrade of HEAT Reporting Services, and will occur when either navigating from the Metrics Server tab of the System Configuration Wizard to the SQL Reporting tab (when reporting is installed on the Application server) or immediately upon launching the system configuration wizard (when reporting is installed on the SQL server)
A Microsoft issue causes the SSRS Instance name to be different between the registry and WMI, when the instance name contains a special character (typically an underscore [_]).
The full solution for this issue is to uninstall HEAT Reporting services, create an SSRS instance with no special characters in the instance name at all, and re-install HEAT Reporting Services module.
Some customers have been able to work around the issue by simply uninstalling and reinstalling the HEAT Reporting Services module, but we recommend the above.
Note: You need not point to that instance and lose previous reports -- The new instance simply creates a consistent value in WMI and the registry, allowing HEAT to reference it properly.