Make sure that the user's Customer Center role has at least View level of access to Track Messages permission. To add the permission:
1. Navigate to Setup > Users/Roles > Manage Roles.
2. Edit the Customer Center role.
3. Under Permissions tab > Lists subtab, add Track Messages and set Level to at least View.
4. Click Save.
Note: By default, the standard Customer Center role has Track Messages permission level set to View.