You hopefully have an update task going to all machines to update the dats.
You can create a dashboard to show all dat versions that are being managed and look at the older ones there.
I have one dashboard query that i run that shows any agent that has checked in in the last 4 hours that isn't compliant. If I know it is talking to the server, then I can address it from there. But if a machine has been offline for 2 weeks, it won't have updated dats, so you have to find the ones that are online and still not updating.
That might not help much, but your issue might be more than a support forum can address easily.
How did you add this query to the dashboard? I have a query showing the info, but I can't drag it to my dashboard?