I had issues with the upgrade of the Software Management Solution Plugin to HF2 (7.6.1505):
1. The policy was enabled already.
This normally mean it does not have a new GUID and did not (re-) run on the Notification Server. I had to start the task manually on the Server for it to upgrade the plugin.
2. The Filter "Windows computers requiring Software Management Plug-in upgrade" is not targeting the correct version, so no client did update the plugin.
AND ( s.[Product Version] LIKE '7.0.%' OR -- SMSAgent 7.0
s.[Product Version] LIKE '7.1.%' OR -- or SMSAgent 7.1
s.[Product Version] LIKE '7.5.%' OR -- or SMSAgent 7.5
(s.[Product Version] LIKE '7.6.%' AND s.[Build Number] < 1409) ) -- or SMSAgent 7.6 1505
it should be < 1505 ... the 1505 is only written in the comment.