Grafana dashboard doesn't display data in Rancher UI
Prometheus is necessary component for using Grafana.
You can check this blogpost:
Kubernetes Monitoring with Prometheus, Grafana and Rancher
Prometheus is an open-source application for monitoring systems and generating alerts. ... Prometheus will scrape targets at designated intervals and store the information in a time-series database.
Grafana is also open source and runs as a web application. ... Grafana makes it easy to create graphs and assemble those graphs into dashboards.
Check, if check if Prometheus is turned on and whether it is configured correctly:
Configuring Project Monitoring
From the Global view, navigate to the project that you want to configure project monitoring.
Select Tools > Monitoring in the navigation bar.
Select Enable to show the Prometheus configuration options. Enter in your desired configuration options.
Click Save.
Also check these settings:
Enable Persistent Storage for Prometheus Whether or not to configure storage for Prometheus so that metrics can be retained even if the Prometheus pod fails.
Enable Persistent Storage for Grafana Whether or not to configure storage for Grafana so that the Grafana dashboards and configuration can be retained even if the Grafana pod fails.