Make sure that the initial configuration is correct, all the permissions are accorded, and the MyInsights Dashboard is visible.

If the Dashboard is visible and the configuration looks correct, be sure that the Simulator is not showing any error messages that could cause the problem.

If there are no error messages in the Simulator, check if there are accounts assigned to the user's territory.

The queries below can be used:

SELECT Id 
FROM ObjectTerritorry2Association 
WHERE ObjectId = '<account id>' AND Territory2id = '<territory of the user>'

SELECT Id, Name, Account_vod__r.Territory_vod__c 
FROM Call2_vod__c
WHERE Territory_vod__c = '<territory of the user>' AND
Call_Date_vod__c >= <start of time period>
AND Call_Date_vod__c <= <end of time period>
AND Status_vod__c = 'Submitted_vod'

If the queries do not return any value, there might be no accounts in the user's territory, and that can cause the Territory Insights Report to be empty.

Note: If viewing the Territory Insights dashboard in Lightning, the report can only query up to 4500 accounts across all territories to which the user has access. If the user has access to more than 4500 accounts, the dashboard cannot display information, as the query hits a Salesforce maximum and fails behind the scenes. 

Related Documentation:

CRM Online Help Documentation:

• Using the Territory Insights Visualization
• Viewing MyInsights Content in Lightning