Scheduled tasks fail with error "Task schedular service is not available"

This article helps resolve the issue in which your scheduled tasks fail to run with error "Task schedular service is not available."

Some of your scheduled tasks fail to run. When you open Task Scheduler to investigate the failure, you receive the following error message:

Task schedular service is not available. Task Scheduler will attempt to reconnect to it.

This issue is caused by the following reasons:

• Incorrect scheduled task configurations.
• Scheduled task target application or script is no longer available or valid.
• Incompatible scheduled tasks after recent operating system (OS) upgrade.

Use the following steps to resolve the issue:

1. Clean up at tasks if they exist.
2. Delete corrupted tasks and then create them again if needed.

Step 1: Clean up at tasks if they exist

Check the C:\Windows\System32\Tasks folder to determine if you have any at tasks created under Task Scheduler. If so, the tasks are listed under the following locations. For example:

• C:\Windows\System32\Tasks

  • C:\Windows\System32\Tasks\At1
  • C:\Windows\System32\Tasks\At2

• C:\Windows\Tasks

  • C:\Windows\Tasks\At1.job
  • C:\Windows\Tasks\At2.job

To resolve this issue, clean up the legacy tasks by using the following steps:

1. Stop the Task Scheduler service:

   1. Download PsTools and extract the file.

   2. Go to the extracted PsTools directory and run the following command from an administrative Command Prompt (cmd.exe) window:

      psexec.exe -s -i cmd.exe
      

   3. After you accept the end-user license agreement (EULA), another cmd.exe process opens. Type whoami in the command prompt, and you should receive the output nt authority\system.

   4. Run this command:

      net stop schedule
      

2. After the Task Scheduler service is stopped successfully, delete the files for at tasks after backup if they exist. Here are some examples:

   • C:\Windows\System32\Tasks

     • C:\Windows\System32\Tasks\At1
     • C:\Windows\System32\Tasks\At2

   • C:\Windows\Tasks

     • C:\Windows\Tasks\At1.job
     • C:\Windows\Tasks\At2.job

3. Clear the schedule entries from the registry:

   1. Open Registry Editor as administrator.

   2. Go to HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Schedule\TaskCache\Tasks, and back up the Tasks folder before proceeding with the next steps.

   3. Delete the keys ending in {1}, {2}, {3} … or more if they exist. Those keys have the property Path set to \\At<#>, for example:

      • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Schedule\TaskCache\Tasks\{1}

        Path=\\At1

      • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Schedule\TaskCache\Tasks\{2}

        Path=\\At2

   4. Delete the following keys if they exist:

      • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Schedule\TaskCache\Tasks\{xxxxxxxx-EC79-4064-9831-xxxxxxxxxxxx}
      • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Schedule\TaskCache\Tasks\{xxxxxxxx-FB9E-4BDD-8FED-xxxxxxxxxxxx}

   5. Go to HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Schedule\TaskCache\Tree, and delete the keys ending in At1, At2, At3 … or more if they exist. Those keys end with At<#>, for example:

      Important

      Back up the Tree key before proceeding with the next steps.

      • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Schedule\TaskCache\Tree\At1
      • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Schedule\TaskCache\Tree\At2

4. Go back to the command prompt opened using the psexec command, and then run the following command to start the Task Scheduler service:

   netsh start schedule
   

Step 2: Delete corrupted tasks and then create them again if needed

If you clean up the at tasks or you don't have at tasks, you might have corrupted tasks that cause this issue. Find the corrupted tasks, delete them, and then create them again if needed.

1. Find the corrupted tasks:

   1. Open Task Scheduler, and acknowledge the first error message to get into the Task Scheduler console.

   2. Expand the Task Scheduler Library structure.

   3. Select each folder object and observe if any of them produce the following error message:

      The selected task "{0}" no longer exists. To see the current tasks, click Refresh.

   4. Take a note of each task that produces this error message.

   5. Once you go through all folders and subfolders within Task Scheduler, you're ready to delete the corrupted tasks.

2. Delete the corrupted tasks:

   Important

   This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For protection, back up the registry before you modify it so that you can restore it if a problem occurs. For more information about how to back up and restore the registry, see How to back up and restore the registry in Windows.

   Note

   Before you proceed with the following steps, back up the following items:

   • The folder %SYSTEMDRIVE%\Windows\System32\Tasks
   • The registry key HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Schedule\TaskCache\

   1. Delete the task file that corresponds to the corrupted task from the Tasks folder (%SYSTEMDRIVE%\Windows\System32\Tasks).

   2. Go to the registry subkey HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Schedule\TaskCache\Tree. Note down the Id value (in GUID format) of each task that needs to be deleted corresponding to the corrupted task.

      Delete the registry subkey that corresponds to the corrupted task from HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Schedule\TaskCache\Tree.

3. Delete the registry subkey that corresponds to the corrupted task from HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Schedule\TaskCache\Tasks.

4. Delete the registry subkey that corresponds to the corrupted task from one of the following locations:

   Note

   The task exists in only one of the three locations and is in GUID format.

   • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Schedule\TaskCache\Plain
   • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Schedule\TaskCache\Logon
   • HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Schedule\TaskCache\Boot

Contact Microsoft Support

If the preceding steps can't resolve the issue, contact Microsoft Support for further assistance.