HPDM 4.7 SP10 not recognizing T420 thin clients

I have few hundreds of T420 thin clients running ThinPro 5.2.0 and agent 4.7.3670.25932.

They are all listed under HP ThinPro5 in HPDM 4.7 SP10 . Last week I received a new batch of same model T420 but the agent version is different 4.7.3674.29393. These thin clients are showing as Unidentified in HPDM.

Any idea why these thin clients are showing as Unidentified ?