A LLD rule is in unsupported state with error "Cannot obtain root\webAdministration WMI service."
The error is generated in zabbix sources ("Cannot obtain %s WMI service.", wmi_namespace)
That's the reason why it did not discover items.

You could check what namespaces in WMI/root do you have. Open powershell and execute this command:

gwmi -namespace "root" -class "__Namespace" | Select Name

"webAdministration" entry should be listed there.
If it's missing then make sure that you have these 2 options enabled on the windows machine:

You can find that on Control Panel > Programs and Features > Turn Windows features on or off.
Without those options I had not "webAdministration" entry on my test windows box.

This should be reflected on the solution doc page
https://git.zabbix.com/projects/ZBX/repos/zabbix/browse/templates/app/iis_agent