Starting from Halo: Reach and going back my service records are not showing up. I’ve been playing Halo since Halo 2 but It is only showing my Halo 4 service record.
I’d guess that you’ve recently changed your gamertag recently. If you load up the games that are missing and play a match or 2 or some campaign, after a while the server should sync everything up with your new gamertag - just make sure to be connected to xbox live 
I shoudl not though that your Halo 2 stats won’t pull over, as the original Xbox Live multuplayer servers are no longer operational