The SharePoint Health Analyzer detected an error.

The SharePoint Health Analyzer detected an error.  PowerPivot: MidTier process account should have 'Full Read' permission on all associated SPWebApplications.

Solutions :

1. Open SharePoint central admin with administrator permission
2. Select Manage services on server from Application Management

3. On the Central Administration page, click on monitoring

4. On the monitoring page, click on review rules definitions
5. Search for the Power Pivot MidTier process account should have 'Full Read' permission on all associated SPWebApplications rule

6. Click on the rule to open on the rule page click on edit items

7. On the rule editor page. Select the repair automatically check box and save.

Now Error should not occur.