How is this different than the green light on the device object properties?
[DEBUG] [06/02/2010 16:18:42.262]  [ZenworksWindowsService]  [aubmn] [Status Library]  [SetStatus: sql= insert into zstatus(timestamp, userguid, objectguid, source, objecttype, operationtype, operationstatus, successcount, failurecount, objectversion ) values ( 634110851222622528,'','',1,'U','Device.Refresh','S',32,0,0)]  
The times in the database are not updated until the status is rolled up which happens every 30 minutes by default. So it could take up to about 5 minutes for the last full refresh time to be updated. However, the last contact time is also set when the device registers. This means it will be updated during the refresh and it is not necessary to wait for the status to be rolled up.
The green light on the device object properties means that the agent is running and listening to this quick task request from primary: http://deviceaddress:7628/RURunning.
This TID primarily aims to define the definitions of Last Contact and Last Full Refresh. Finding the cause of problems with their updating is beyond the scope of this document.
If the last full refresh time never gets updated the problem could be in the roll up of the status. In zmd-messages.log. Search for "StatusSender" and "Status Sender". If the status sender is not logging any problems then perhaps there could be an issue on the server. Search the services-messages.log and loader-messages.log for "The Device can not be updated with the last full refresh time" or "[status" errors.