You would need to make the leaver a current active fee earner again to enable you to run these reports. Please follow the steps below:
From the DPSSQLConfig (requires user with Supervisor rights), selected Users and Groups tab.
Select Users from the left-hand navigation pane, then click Show Leavers.
Double click on the fee earner
Under the Main Details tab, tick Is active and Is Fee Earner.
Under the Extended Details tab, remove the Date from the Date Left Company field.
Click OK.
You will now be able to run reports picking up this user as a Fee Earner. Once complete, add a leaving date and untick the user from being a Fee Earner and from being Active, then click OK.