You are trying create a Task Server on a Windows 2016 Server. The "Task Service" button is grayed out. Also, you see the following hover message.
Task Service
Requirements:To install the Task Service, the computer must meet the following requirements:
Managed by this Notification Server
The latest version of Symantec Management Agent installed
Microsoft Internet Information Services (IIS) configured.
Microsoft .NET Framework Installed (one of the versions from 4.5.1 to 4.7)
Running on one of the Supported operating systems.
Windows Server 2016
Symantec IT Management Suite 8.x
Microsoft deprecated the Application Server Role starting in Windows Server 2012 R2 --> Features Removed or Deprecated in Windows Server 2012 R2.
The needed features are now included with the installation of Web Server (IIS).
On your Site Server open the "Server Manager" and click on "Add roles and features". You will see the following.
Click "Next"
Choose "Role-based or feature-based installation" and click "Next"
Select the Site Server from the "Server Pool" and click "Next"
Check the "Web Server (IIS)" box.
The following appears.
Click on "Add Features".
Click "Next". The following will appear.
Click "Next". The following will appear.
Click "Next". The following will appear.
Click "Next". The following will appear.
Click "Next". The install will begin. When it is finished you will see the following.
Click "Close" and then restart the server.
Now when you open the Symantec Management Console and go to Settings>Notification Server>Site Servers, click New>Site Server, choose your server you will see that the "Task Service" box is no longer grayed out.