SEP Manager not showing client scans

I am having issues with the SEP Manager database not properly reflecting that clients have successfully run their scheduled scans.  This occurs for 100% of the machines I manage, which is 78.  I have checked the machines and they all say that their scans have completed, but in the Manager it says the last scans were months ago.  Not quite sure where to go from here.  Currently running SEP 11.0.5002.333