There are 3 possible reasons why the Resolved section may be disabled:

1. A grievance cannot be resolved before the Follow Up section is complete. 
2. A user can only Resolve a grievance if the user is granted the permission "Resolve Grievances" under Settings>User>Apps>Grievance Log. See User Settings and Permissions.
3. Once the resolved section was completely filled out and saved, it can only be edited if the user is granted the permission "Edit Grievances" under Settings>User>Apps>Grievance Log. See User Settings and Permissions.