Step 1.Send them massages using the SFI mailer.Step 2. Send them mails by using genealogy mails. Step 3. Try to get hold of their personal email addresses and start communicating with them personally if this does not work go to the next step.Step 4.if you have their telephone numbers start calling them if this does not work go to next step.Step 5. Reassign them and try with new ones better experience and you are on track again
good luck