VS402325: Work item type category Microsoft.HiddenCategory does not exist in project

I am trying to create a new TFS vNext build definition in TFS 2015, and for one of my Team Projects I get this error when trying to create a build:

500: VS402325: Work item type category Microsoft.HiddenCategory does not exist in project [TeamProjectName]

I have previously created XAML builds on this Team Project, and vNext builds on other Team Projects on this server. There must be something wrong with how this Team Project is set up, but I can't figure it out, and Googling this error gives me nothing.

I thought exporting the Categories might give me a hint, but HiddenCategory isn't being used (is it suspicious that this output is missing some types, such as "Task"?).

Did you upgrade from previous version of TFS? If it is, make sure you have done Configure features after an upgrade

According to the error message, there is no Microsoft.HiddenCategory in the Categories.

The easiest way to get this fixed is to export the categories from a normal Team Project, and then import them to current failed team project:(Backup the Categories.xml file first in case meet other issues.)

witadmin exportcategories /collection:http://MyTFS:8080/tfs/DefaultCollection /p:Project1 /f:”C:\temp\Categories.xml”

witadmin importcategories /collection:http://MyTFS:8080/tfs/DefaultCollection /p:Project2 /f:”C:\temp\Categories.xml”

---

If that not work, you could try to add the category manually by the following steps: Reference Update a team project manually to support test management for details. (Update your category definitions area.)

1, Export your categories definition file.

witadmin exportcategories /collection:CollectionURL /p:ProjectName /f:"DirectoryPath\Categories.xml"

2, Add the Microsoft.HiddenCategory category and add the new WITs to the hidden category (Based on the requirement of your team project).

<CATEGORY name="Hidden Types Category" refname="Microsoft.HiddenCategory">  
    <DEFAULTWORKITEMTYPE name="Code Review Request" />  
    <WORKITEMTYPE name="Code Review Response" />  
    <WORKITEMTYPE name="Feedback Request" />  
    <WORKITEMTYPE name="Feedback Response" />  
    <WORKITEMTYPE name="Shared Steps" />  
    <WORKITEMTYPE name="Shared Parameter" />  
    <WORKITEMTYPE name="Test Plan" />  
    <WORKITEMTYPE name="Test Suite" />  
  </CATEGORY>  

3, Import the updated file.

witadmin importcategories /collection:CollectionURL /p:ProjectName /f:"DirectoryPath\Categories.xml"