This report should work for you:
Select tblAssets.AssetID,
tblAssets.AssetName,
tblAssetCustom.Manufacturer,
tblAssetCustom.Model
From tblAssets
Inner Join tblAssetCustom On tblAssetCustom.AssetID = tblAssets.AssetID
Where tblAssetCustom.Model Like 'Latitude%' And tblAssetCustom.State = 1 And
Not Exists(Select tblSoftware.AssetID
From tblSoftware Inner Join tblSoftwareUni On tblSoftwareUni.SoftID =
tblSoftware.softID
Where tblSoftware.AssetID = tblAssets.AssetID And
tblSoftwareUni.softwareName Like '%BIG-IP Edge Client%')
Order By tblAssets.AssetName