Sharepoint report dashboard access denied error

If you try accessing a dashboard you've created, but instead of getting data you receive an Access Denied error that looks like this

you can fix this by adding the site responsible for holding the data source to the reporting site's trusted locations. To do this:

1. Log in to the Sharepoint central administration

2. From there, go to Application Management

3. Under the Office Sharepoint Server Shared Services section, click on "Create or configure the farm's shared services"

4. Click on SharedServices1 (or whatever you named your shared service process instance)

5. Under the Excel Services Settings section, click on "Trusted file locations"

6. Click on "Add Trusted File Location"

7. Fill out the information listed, directing it to the Sharepoint library you would like to use for your data source. The settings have descriptions and should be self-explanatory

8. After you have your trusted location setup, go back to your reporting page and refresh. Your KPI's, reports, and whatever else should now load correctly since the site can access the data at this point

For the TechNet article, you can find it here