WMI counter for MS SQL Server returning zero

WMI counter for MS SQL Server returning zero

I have added a WMI counter for SQL  Server as a performance monitor and used
SQL Server: Database mirroring
log send queue db
then selected the _Total instance
 
If I watch this counter in perfmon I can see the value increasing but OpManage always returns 0
Have tried this upon a simple SQL server, named instance and cluster - all 0
 
How can I monitor this value?
 
Mike

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