Q:

VS2019 Custom template not shown

I have created a custom template for VS2019 that contains two projects. Below is my root.vstemplate file
<VSTemplate Version="3.0.0" Type="ProjectGroup" xmlns="http://schemas.microsoft.com/developer/vstemplate/2005">
  <TemplateData>
    <Name>Asp.Net Core Template EF Core</Name>
    <Description>Asp.Net Core 3.1 Boilerplate template</Description>
    <ProjectType>CSharp</ProjectType>
    <ProjectSubType>
    </ProjectSubType>
    <SortOrder>1000</SortOrder>
    <CreateNewFolder>true</CreateNewFolder>
    <DefaultName>Asp.Net Core Template EF Core</DefaultName>
    <ProvideDefaultName>true</ProvideDefaultName>
    <LocationField>Enabled</LocationField>
    <EnableLocationBrowseButton>true</EnableLocationBrowseButton>
    <Icon>logo.png</Icon>
  </TemplateData>
  <TemplateContent>
    <ProjectCollection>
      <ProjectTemplateLink ProjectName="AspNet Core Ef Core">
        src\AspNetCore3EfCoreTemplate\MyTemplate.vstemplate
      </ProjectTemplateLink>
      <ProjectTemplateLink ProjectName="AspNet Core Ef Core Web">
        src\AspNetCore3EfCoreTemplate.Web\MyTemplate.vstemplate
      </ProjectTemplateLink>
    </ProjectCollection>
  </TemplateContent>
</VSTemplate>

I followed the instructions of this link but my template is not shown when I try to create a new item in VS2019. Anyone knows why is this happening?

A:

I followed the instructions of this link but my template is not shown
  when I try to create a new item in VS2019. Anyone knows why is this
  happening?

For the custom project template, the new VS2019 UI for creating projects cannot find custom project templates through filters and these templates actually exist in it.
All Langages, All Platforms and All Project Types and the search box lose the ability to filter custom project templates and this is a known issue in VS2019. But it still happens in the latest version VS2019 16.4.2. If you want to solve this annoying problem, you can report an issue to DC Forum to report this abnormal behavior for support. This might be a long process or you can try my suggestions below:
Suggestion
1) Do not use any filters in VS2019 Project UI and then drag to the bottom of all templates to find the custom template, which is usually inserted after all the default templates.

This picture shows it at the bottom of all templates.
2) change to use VS2017 which has no error about this.
Update 1
l have created with your further info and test in my side without any errors, my environment:
win10 enterprise 1903; VS2019 Community 16.4.2
My Steps:
1) l have created two projects into a same solution: 
a Net Core 3.1 ClassLibrary project and a ASP.NET Core 3.1 Web Application project.
2) then click Export Template.. in the Project menu and export these projects as project template separately.
3) open the folder and unzip them into the same folder called src. 
This shows the two unzip project folders in the src folder

Then, this shows the final form of the folder,and src folder contains the two project folders as the picture shows above

4) root.vstemplate is the code you provide. The project Template is called Asp.Net Core Template EF Core as you said. After that, I compress these two files into a package called multiple projects template,and then put this zip file into this path C:\Users\xxx\Documents\Visual Studio 2019\Templates\ProjectTemplates.
5) then I close VS Instance and then restart VS and clear all the filters and then pull the project templates to the bottom, and then look up at the bottom for a template called Asp.Net Core Template EF Core.
> l have found this template in my side and if you does not see this, please repair VS and then disable any third-party extensions in the Extension-->Manage Extension menu to prevent interference with VS. Besides, since your VS is 16.4.1, you could try to update it to 16.4.2.
Update 2 
With your sample, l think l found the issue. The issue is that root.template cannot find the two contained projects:
You put root.template in the Src folder and the root.vstemplate file write these:
src\ClassLibrary1\MyTemplate.vstemplate

src\WebApplication3\MyTemplate.vstemplate

It uses relative paths to find these files and the current path where your root.vstemplate is located does not have src so it cannot find.
The solution is that you should put root.vstemplatein the same directory as the SRC folder and then compress these two. After that, put this Multiple.zip into C:\Users\xxx\Documents\Visual Studio 2019\Templates\ProjectTemplates.

Hope it could help you.

