Hi,
There is a bug fix in SEP 12.1 RU6 & details are as per below. See if it applies in your case or not.
Cannot enable "Include only clients that have checked in with the management server today" in SEPM
Fix ID: 3646594
Symptom: You cannot enable Include only clients that have checked in with the management server today in the Virus Definitions Out-of-date notification.
Solution: A new notification type in 12.1.5 (12.1 RU5) inadvertently overwrote the setting that stores the check box selection for out-of-date content notification conditions. This issue has been corrected.
Reference: http://www.symantec.com/docs/TECH230558