It generally happens during upgrade or restructuring of SMS/SCCM infrastructure. Anyway, if it happens with you, try below steps-
1. list out all these clients or make collection of these clients
2. run script to trigger discovery data collection cycle on listed machines or use right click tools to initiate discovery data collection cycle on machines listed in collection
3. once you have finished with above two actions, try update collection membership and refersh then.
4. Check status and make yourself happy.
Pls find link to download right click tools.
and here's script to initiate discovery data collection cycle on affected clients-
'copy below code to notepad and save it as discovery.vbs
'and run remotely on clients with help of psexec.exe utility
actionNameToRun = "Discovery Data Collection Cycle"
Set controlPanelAppletManager = CreateObject("CPApplet.CPAppletMgr")
Set clientActions = controlPanelAppletManager.GetClientActions()
For Each clientAction In clientActions
If clientAction.Name = actionNameToRun Then
wscript.echo "Executed: " & actionNameToRun ' if you want to get message
these are some more actions which can be used in above script as and when required-
'Software Metering Usage Report Cycle
'Request & Evaluate Machine Policy
'Updates Source Scan Cycle
'Request & Evaluate User Policy
'Hardware Inventory Collection Cycle
'Software Inventory Collection Cycle
'Software Updates Assignments Evaluation Cycle
'Peer DP Maintenance Task
'Machine Policy Retrieval & Evaluation Cycle
'MSI Product Source Update Cycle