Hi, you can use tactics that all succesfull SFI members uses, and that is helping them almost 24/7, if they feel neglected they will not continue their jobs, but if you contact them at least a twice a week, or more, you should be able to motivate them. Also great motivation is to share some rewards with them , like reassigning CSA's etc.
And the great advice for all team leaders is : never give up on someone, give them your best, help them always by any means neccesary !
Cheers...