On some occasions, Metric Explorer is unable to load data with the error "Whoops! Some data could not be loaded", as shown in the following illustration.
The issue could be due to the instance losing the connection to MetricBase for some reason.
You can verify the MetricBase connection by using the MetricBase Configuration module.
Go to https://<instance_name>.service-now.com/sys_clotho_config_list.do?sysparm_query=.
Access the "clotho" record.
Run the test connection via the UI action Test Connection.