Symptoms:  A new SMP server was installed, but configured to use a restored backup from the original database used by another server.   The reconfiguration seemed to go well, and the console was able to open the database and render the tree and objects with no apparent problems, except that a newly configured Task Server could not be connected to. The new Task Server could not even connect to its self.  It would instead connect to the SMP, which also is a Task Server.

Also, the Task Servers were not posting to the page "/Altiris/TaskManagement/ClientTask/ExecTSMethod.aspx" which is how Task Servers register as valid Task Servers with the NS and update their current status and information. No servers were showing as updated in the database.  The following SQL query, run against the Symantec_CMDB database will show if this is the case:

select c.Name, cts._ResourceGuid, cts.IsActive, cts.Version, cts.LastRegistered, cts.LastTaskCheck, cts.NSGuid,DATEDIFF(dd, cts.LastTaskCheck, getdate()) [Days Since Last Registration]
from Inv_Client_Task_Servers cts
join vComputer c on c.Guid = cts._ResourceGuid
order by 1

Also, the following  three warnings/errors (something like it) that were constant in the logs of the new Task Server as well as clients that were manually assigned to it.

Description:
  Operation 'Direct: Post' failed.
Protocol: HTTP
Host: SS-Parent.yourdomain.local:80
Path: /Altiris/ClientTaskServer/Register.aspx
Id: 118.3272
Error type: SMP Server error
Error code: The server is currently paused (0x8004200E)
Error note: HTTP Status 200: 200 OK

Source: Client Task Agent
Description:
    Failed to call web interface by url [http://SS-Child2.yourdomain.local:80/Altiris/ClientTaskServer/Register.aspx?lastResort=true&resourceGuid=fd3ebae7-3929-4004-b39b-570fd638cc5b&crc=00080001000013E0], error [0x8004200E, IDispatch error #7694].

  Description:
    Could not register using "http://SS-Child2.yourdomain.local:80/Altiris/ClientTaskServer/Register.aspx"

 Source: Altiris.ClientTask.Server.ClientTaskServer.ReRegister
Description:
  Failed to perform re-register.
Error response returned from server: The handler 'RegisterTaskServer' is failed to process request. Computer fd3ebae7-3929-4004-b39b-570fd638cc5b trying to register as a task server (version: 8.1.5053) on NS 8b346aa0-f9e3-4001-b9bb-53c77df42e0c is not registered as a site server on NS. It may be temporary situation until collections update on the NS is performed. Please make sure that this computer is registered on NS as site server. In case of disaster recovery scenario, run 'NS.Restore Task Servers' Windows Schedule.Request: source=195.168.5.100, version=<legacy>, size=0, page=RegisterTaskServer.aspx
   [System.Exception @ Altiris.ClientTask.Server]
   at Altiris.ClientTask.Server.Communication.NotificationServerWebConnection.CheckResponseForFailure(WebResponse webResp, Stream respStream, StreamReader respStreamRdr, XmlTextReader respXmlTxtRdr)
   at Altiris.ClientTask.Server.Communication.NotificationServerWebConnection.PostToNotificationServer(String url, NSWebConnectionBuildRequestStreamDelegate requestStreamDelegate, Stream& respStream, StreamReader& streamRdr, XmlTextReader& xmlTxtRdr, Boolean& dataEncryped, Int32 nMaxAttempts, Int32 nTimeout)
   at Altiris.ClientTask.Server.Communication.NotificationServerWebConnection.RegisterTaskServer(Guid serverGuid, Guid resourceGuid, String version, Int32 build, Nullable`1 httpPort, Nullable`1 httpsPort, TaskServerConfiguration& tsConfig)
   at Altiris.ClientTask.Server.ClientTaskServer.RegisterTaskServer(Version taskServerVersion)
   at Altiris.ClientTask.Server.ClientTaskServer.ReRegister(Version taskServerVersion)

Symantec Management Platform 8.x

In this case the master URL in the "Task Service Settings" Policy was pointing to the original SMP server, and not the current one.  As a result the new Task Server was contacting the old server and, since the old server did not recognize the requesting TS, it replied with nothing.  The Task Server therefore interpreted that it was currently in a paused state and, or inactive.