The Package Server Agent plugin is out of date. Where in the SMP Console can you find the policy to update it?
ITMS 8.6 RU1
The Windows Package Server Agent Upgrade policy is found in the SMP Console at either of the following locations and you can verify it is enabled and properly configured here:
Settings > All Settings > Notification Server > Site Server Settings > Package Service > Advanced > Windows
Settings > Notification Server > Site Server Settings > Package Service > Advanced > Windows