Hi Paul,
Correct Upgrade path is to upgrade the agents by using upgrade policies. Pluggable Protocols Agent (PPA) is a part of the Remote Monitoring Server (RMS) package which is distributed by Windows Remote Monitoring Server Upgrade policy.
Based on screenshot I have not understand why you have PPA without RMS on selected machine...
Also based on same screenshot your PPA have correct version. In SmpVersion table in DB is incorrect version (from 8.1 GA). Seems that by some reason configuration of the PPA 8.1 HF4 was not executed or executed but not fully.
You might try to execute the configurationa of the PPA 8.1 HF4 manually by using aexnsconfig.exe (http://www.symantec.com/docs/HOWTO6681):
example: C:\Program Files\Altiris\Notification Server\Bin>AeXConfig.exe /configure "C:\Program Files\Altiris\PluggableProtocols\Config\PluggableProtocols.config”
But do so at your own risk.
If you want help with that please contact customer support.
Regards,
Dmitri