Update 2中的警告消息应该是原因.自动链接工作"功能比较当前版本和先前版本之间的更改和工作项.当更改或工作项的数量大于200时，将不会链接.创建新的构建定义并运行构建时，没有以前的构建，这意味着将计算代码存储库中的所有更改和工作项.而且，如果在后续版本中的更改没有任何更改或未链接任何工作项，则它也不会链接任何工作.

The warning message in your Update 2 should be the reason. "Automatically link work" feature compares the changes and work items between the current build and previous build. When the count of changes or work items is more than 200, it will not link. When you create a new build definition and run a build, there is no previous build which means that all the changes and work items in your code repository are calculated. And also if there is no change or no work item linked in the change in the subsequent build, it will not link any work either.