Hard to say given these details. The obvious things to check are community strings and ACLs. That is, perhaps you have a community string ACL on your switches that is allowing the LMS 2.2 server to query the devices, but not the 2.5 server.
Your best bet for finding the cause of this problem is to enable vmpsadmin debugging under Campus Manager > Admin > Data Collection > Debugging Options, then run a full User Tracking acquisition. Then open a TAC Service Request and include the ut.log along with a sample MAC address that is showing up in 2.2 but not in 2.5.