Site server showing not registered

[xrtech]

We have several site servers with the Task and Package services installed. 

A couple of them are showing as being Not Registered on the Task Status tab.  A couple more are pointing back to the Notification Server as the Task Server.

I have triple-checked that the subnets are correct and that the subnets are assigned to the correct site and the sites targeted by the proper site server.
Is there somewhere else I should be checking?

Also, what is best practice?  Should a Site server be targeting itself as the Task Server if it has the Task services installed?

[xrtech]

I wanted to add that under the Agent Settings tab on the site server Management Agent, the Notification Server information is correct., and it is showing that it is connected to the Notification Server.