Job, Host and Port are all empty for Node Exporter

Hi,
I have Prometheus set up to scrape the Node WMI data. I added the Prometheus data source to Grafana, and the Prometheus dashboard works fine. But both Node Exporter Full and Node Exporter Server Metrics are blank and the dropdown menus at the top are all empty for Job, Host and Port.

Anyone know how I can fix this?
Thanks!